For me, its sometimes hard to urinate while stoned, even if i really have to go. I figured that it was all mental, as when im really stoned, it reminds me of dreaming, so i figure that my mind doesnt want to let the flow go because it thinks i might be peeing myself. It takes some concentration, but i just try to slow my heart rate/take deep breaths, and just try to relax.

So like someone already mentioned, maybe it could be mental?..and yeah, stressing about it doesn't help either. Like when you masturbate and worry too much about cumming, you'll probably cum right away, right? :P