New Experience While Dildo-ing Solo

I encountered a new sensation while doing some solo dildo play the other night. Typically I use it hands free while suction cupped to my dresser, going on my hands and knees. I've always found the feelings to be quite enjoyable, although I've never experienced any sort of 'O' from it (Dry, Wet, Super or whatever). This session was a bit different though; my sphincter felt more relaxed than usual and I was experiencing a very warm sensation near the inner anterior part of my anal passage - no doubt it was my prostate becoming engorged.

I would have very much liked to continue the session to the point of 'O' but I found things sort of fizzled out after I tried to manually finish myself off with a traditional 'O' while simultaneously using the dildo. As soon as I started stimulating my penis, my anus reacted and tightened up and I wasn't able to continue with the same great sensations I was getting while it was relaxed. Plus I had just finished a session with my aneros device so I was still leaking a bit of lube from that session and I was a little concerned about making a mess.

Next time I'll have to make sure I'm sufficiently cleaned out before I start a session with the dildo again. The threat of any sort of leakage or mess seems to be a real deterrence from being able to be sufficiently relaxed and care-free during a session.

Comments or advice appreciated!