I experienced this once, following a suicide attemt, when I took over 100 Nurofen Plus pills. Next day, in hospital (ahem!) I felt like I needed to go... but once in the bog, nothing. Go on, go on... WTF? Thinks "must be the codeine? dammit, no pathetic over the counter drug beats me! Go on... come ON before I fucking explode!" THen a more sensible thought. "Hey, chill out... just relax, don't worry about it... if you need to piss, you'll piss... be patient, let nature take her course..." I was eventually rewarded with a steady stream and many sighs of relief. Bad, bad moment though! Good luck...