She had always wanted to try and I was excited by the thought. She is 25 and I'm 34. We met an older couple online (both 40s I think) and went to theirs.

The guy was so confident and dominant that it really threw me, my gf immediately took to him and behaved in such a hot, submissive. She let him do whatever he wanted and seeing it made me cum all over myself as I was barely undressed. The women I was with was lovely and sympathetic but I got so insecure. She ended up taking me into the shower to have fun and clean up but I couldn't stop thinking about my gf with him. He lasted so long and went multiple rounds. I couldn't compete at all. I've never seen her happier.

I can live with being not him but any ideas how I keep my composure myself in future?