thats funny, cause when I was getting certified last year, I had to pee sooooo bad during one pool session. I tried for about 10 minutes to pee, but I either couldn't overcome to pressure, or I was just too shy, cause I ended up having to hop out of the pool and run for the bathroom.
still haven't had to pee THAT bad again so far, so I still haven't peed in a wetsuit (and I'm not really planning to either, but who knows...)
I've never had trouble peeing during a dive; in fact (and this may be too much info), on my first long boat trip I got so used to letting go whenever I needed to that I came very close to making a big mistake while driving home...