I have to admit I some times have this problem at urinals...nothing to do with size or any thing in my case or been ashamed...

I never have this problem when I am in the corner of the urinal but in the middle with guys next to me..

its pretty awkward when you go up for a piss nothing comes out and you just stand their waiting..waiting...waiting then go and wash your hands and act like you have pissed haha....a few times smart ass guys have even say stuff lol I remember one guy goes bit dry their brother...I was like why are you looking or something along those lines shut him up pretty quick haha

It is defiantly something with you brain thinking it up...usually the best approach is to piss when i am bursting to go that usually works even if their are guys basically squashing into the urinal for space...