Felt a buzzing in my prostate, have I hit a milestone?

Ok so before I start, Holy Smokes was that exciting! I admit I do like the sensations my body makes, from stomach gurgles to involuntary muscle twitches and everything. So to get to it...

A couple nights ago (didn't have internet or I would have posted IMMEDATELY) I was practicing with my Aneros Vice. I'm still a beginner and have done maybe...six or so sessions. I know the rules, no touching, relax, lie on your side and all that. So it came as a really exciting surprise when I was using my Aneros Vice (non vibrating, also suggested not to use until you are a veteran) that when I was using it (about 40 minutes in,) upon a contraction I felt my prostate rapidly vibrate for a second. When that happened I instantly got an excited smile, because I think I hit a milestone and showed that it's working! It felt like I had woken up some ancient machine. Going with it and not forcing it I had two more in session, and then it basically stopped. I didn't really get any feelings elsewhere in my body, just a sort of very fast and quick vibration in what I assume was my prostate gland.
I've heard around that it's your prostate filling up with fluid, but since I didn't see/missed it in the Wiki, I figured I'd ask on here and see what the veterans think it is. Did I just hit a milestone and truly am well on my way to prostate orgasms? Or was it just a regular bodily that didn't actually contribute to the prostate orgasm progress?

(Edit: I forgot to mention that I found I can clench new muscles. It feels like I'm pulling in like you would with the anal muscles but it's just in my rectum, like it's on the sides of the walls. I'm assuming that's a good thing? Makes for lighter contractions)