Worst I had was my best female friend. We'd been friends since the age of 7 and never had so much of a kiss until we were mid-20s. We had a drunken afternoon that turned into a drunken evening back at mine. I got changed in front of her for a dare, she showed me her boobs, one thing led to another and we ended up having sex. It was totally weird and not exciting. I'm not sure I even got fully hard, but strangely came really quickly but tried to carry on and get her to finish. We were totally out of rhythm and there was zero connection. No words spoken during or after, never been mentioned since. Was very awkward and not fun....
She DID give me a handjob on the way back from a night out a few years later. THAT was good
