It could be a bit of both issues. Alcohol can have a big effect on a person getting an errection or not also maybe it could have been the fact that you wanted to be sleeping with your ex and when you realised it wasnt her you got disappointed??

I dont know im only guessing!

Sex is a psychological issue. What's going on in your mind will always have an affect on what's going on with your penis. This is generally a slow realization for guys. We tend to feel like we could all be in porns. Ready to go whenever. You forget movies can be edited.

Drinking makes erections more difficult. Being nervous really kills it. If you were thinking of the other girl, that probably added a little bit too.

Ever seen the episode of Friends where Rachel yells at Ross about his ED? "Its not that common, it doesn't happen to every guy, and it is a big deal!" Yeah, well, that's crap. Its very common, once in a while, but nobody talks about it.

Don't worry about it. You'll wind up with performance anxiety, which I have now with new partners after a particularly horrible, yet mercifully short, relationship.

Not true, it's very possible to get an maintain an erection even if you're not really in the mood. However, a smart wife or girlfriend will figure out if you're not because your testicles will not have retracted up and tightened.

Is there a possibility the thought of your ex is coming up and making you lose your erection because your not going to be having sex with her. Like a form of stage fright to perform with someone new?