Holy shit, I thought I was the only one!
Grosses me kinda out to talk about it, but whatever.
It started for me after recurring listening to Wet to Forget by Mistress Joanne. The first time it felt like two orgasm like sensations with liquid pouring out in exquisite waves, but not anywhere near full pissing. To me it appeared to be precum. After the session I peed like normal and was totally blown away by the experience.
When I finally achieved similar sensations in later sessions, it has resulting in increasing amounts of piss. It's not a bad sensation, the buildup is surprisingly great, but it's so god damn irritating to cleanup! Also it is not what I'm trying to achieve, but thats where I have ended up thus far, frustrating.
Any tips and shared experiences are appreciated!