Long time lurker, some questions

@Rene95 Welcome to the Aneros forum! After reading your post, I realize that you haven't identified the particular Aneros model(s) you are using. Perhaps you may need to go larger (or smaller). Of course, most of our sessions have high expectations. But, IMHO if you shift your focus just a little bit from "what can I do to make it feel better?" to "what am I feeling right now?" you can eliminate the expectations from your thoughts. Just enjoy every little bit of pleasure from wherever it comes. Could be the prostate, the penis, the rectum, wherever. Let your mind drift-off with the pleasure. More pleasure may come to you. You may feel something that you haven't felt before in a session; enjoy it! Don't try to "amplify" it.

Are you familiar with the "do-nothing" technique? Have you tried it? It is always a good start to a session. It may seem ridiculously simple, but sometimes it can lead you to much greater pleasure when you least expect it. Regarding your question about erections, initially just ignore it. If it grows hard during a session, you should also feel it in your prostate. Your penis should be a casual observer in your session, nothing more, nothing less.

I have always savored sexual fantasies during my sessions. While you are in that "sea of pink bliss" what are you feeling? If you let your mind wander, where are you going? Are you doing something sexual with another person? Is someone doing something sexual to you? While in this state, don't even think about doing kegels or other contractions. They will come to you very naturally as your pleasure-feedback intensifies and you won't be able to stop it.

Good luck on your journey and please keep posting! I for one will enjoy reading about your progress!

I mostly use the MGX and now the MGX Trident. I usually try to start my sessions by just relaxing. I lie down and listen to a "differential relaxation" tape I have, then once I'm good and relaxed, I try to focus on the sensations and come up with a fantasy. Sometimes I'll listen to some erotic audio. If/when nothing happens, I usually end up playing around with contractions, which feel nice but don't seem to lead anywhere.

The two times I felt that "sea of bliss" thing, whatever it was, it was so unexpected and good that I got excited and thought "something is happening, this is it!", and I think that killed it. Just wish I knew how to get back to that point.

@Rene95 Sure sounds like you are hitting all the bases. Are you listening to audio during a session or before? It may make a difference. Sometimes, I will listen before a session (including binaurals). Then when I feel like I'm aroused and ready, I'll do a session. The audio during a session may be distracting you and shifting your focus elsewhere. Also, the lube you use may make a difference in the movement and hence, the feelings. Do you have other Aneros model(s) that you can use in rotation? All suggestions IMHO.

I agree with what @goldenboy said above.

I try very hard to let go of my expectations.

I suspect this (expectations) may be at the root of your lack of progress. All your other comments reflect a knowledge of the basic mechanics of Aneros use, which is all well and good but the mechanics are only a small part of the Aneros journey. The largest part is a mental journey and a big part of that is learning to "Just Let Go !". As Yoda famously said "...Try NOT, Do or Do NOT, there is no try!"

Most of my sessions are quite enjoyable.

Your body is responding with pleasure waves, however, you immediately negate it with your "...But I have been stalled and I don't know what to do." statement. This too reflects an attitude of expectation for something more.

What are anal contractions and rectal contractions? I can move the aneros inward... I can kegel. I can try to poop the aneros out. Am I supposed to do all three at once?!

You can't do all three at once, but you can do them sequentially. You may find @CaveOfMystery 's post Quick and Dirty Path to the Super-O informative here.

Am I literally supposed to be doing any or all of these things till my muscles are tired and shaking? Because that does make the aneros move in a lovely and involuntary way, but the aching ab muscles are not enjoyable and I can't keep it up for long.

Using the muscle fatigue technique to induce involuntaries is an effective technique but if it is inducing discomfort then it is going to be self defeating. If you can get to the point of inducing the involuntaries without inducing discomfort then try just holding a contraction for as long as you can at a low level of tension perhaps on the order of 25%-35% of maximum, see where that takes you.

What is a "p-wave"?

From the Aneros WIKI Glossary - "pleasure wave (P-wave) A feeling of sexual excitement and pleasure that normally originates in the lower abdominal and/or pelvic regions. P-waves may be localized or spread out all over the body. Some have suggested that the sensation feels like butterflies in the stomach (but lower in the abdomen) or as the feeling of sexual electricity associated with ones first touch from the first encounter with a lover. As the body becomes more sensitized with arousal amplification, pleasure waves become more common and can be produced by the Aneros or by other arousal amplification techniques. P-waves may be very subtle or intense."

And what does a prostate orgasm actually feel like?

From the Aneros WIKI Glossary - "prostate orgasm (progasm) A non-ejaculatory orgasm focused in and around the prostate. These may be among the most intense non-ejaculatory orgasms. In a certain sense every orgasm is a prostate orgasm on account of the fact that so many sensory nerves are associated with the prostate (either directly or indirectly) and that these same nerves are the ones that are responsible for male sexual arousal. The term prostate orgasm relates to the physical sensation of this kind of orgasm being centered in the prostate. While it may begin there, these orgasms typically branch out and can even turn into a whole-body experience."

I experience tingling in my feet and balls. Sometimes I feel a warmth in my crotch. If I contract hard, I shudder in pleasure. On two memorable occasions, I felt waves of whole body pleasure coming and going, like I was floating in a sea of pink bliss. It lasted a minute or two and was nice, but nothing like the descriptions on here, and I don't know how I did it. Was that a p wave? Was it an orgasm? How the heck do I do it again?

"...a minute or two...floating in a sea of pink bliss." sounds like much more than a simple pleasure wave to me, I'd describe that as a definite Super-O ->"...an orgasm that steps out of the normal frame of reference.". Isn't it possible you have expectations for your orgasm which may be unrealistic and based in some mythic notions generated by other peoples descriptions? Please read the threads What's an Orgasm?, Super-O Myths & Illusions & @neros thread The Myth of Super Orgasm.

Do I have to be hard or incredibly aroused for this? As nice as the aneros does feel, it is difficult to stay hard and aroused for very long...

If by "...have to be hard..." you mean maintain an erection, the answer is NO, your erectile state doesn't matter when it comes to pleasure derived from prostate massage. Some men remain erect, some men remain flaccid, some men cycle between the two states, it doesn't seem to matter. Arousal (see Are you "aroused"?), however, is an important aspect of any Anerosession. without being sufficiently aroused your session is likely to be lackluster at best and a 'dud' at worst. Remember your Aneros device acts much better as an arousal amplifier than an arousal generator. Your mindset is critical for successful Anerosessions, a Zen approach may prove most beneficial. The Tao of Aneros
Orgasmic success is inversely proportional to one's level of expectation.
Orgasmic success is proportional to one's level of arousal.
Orgasmic success is proportional to one's level of patience.
Orgasmic success is proportional to internal body language receptiveness.
Orgasmic success is proportional to the level of mind/body relaxation.
Orgasmic success can not be forced or coerced to occur.
Orgasmic success can be triggered or amplified by multiple stimuli.
Orgasmic success can begin anywhere along the erotic spectrum.
Orgasmic success is the gift of awakened body/mind energies.
Orgasmic success is dependent on trust in body and mind.
Orgasmic success is affected by all life choice practices.
Orgasmic success is achieved following your own unique path.

If you can morph your expectations into intentions,
if you can morph your anxiety into patience,
if you can morph your demands into desires,
if you can morph your mind noise into a mind mantra,
then you're ready for a Super-O to morph into you.

Good Vibes to You !