I think this is the funniest thread on this site! Probably because its happened to all of us at one time (if you're lucky!) or another.
Like so many others on here, anal sex was my downfall as well. I have an ex who used to say "OK" occasionally and I never lasted more than a few strokes. I don't know if it was because it was so tight, or the lengthy struggle rubbing myself along her lubed up crack and false starts to finally get myself inserted, or the sheer novelty of it, but once buried to the balls, I would be like, "OMG. this feels great!" followed by an "Agh!" and "OMG, not again!
