It's common to get nervous after an encounter and would say that getting so drunk that you fear you forget things is not a good or safe practice. I'd cut down on drinking. But since you had a condom and intended to use it, you probably did. Sounds like you would normally so even if drunk, you probably did. But in case you didn't? You test at 5 months negative and that's conclusive. And no a staph infection isn't going to interfere with the result.