Get back on wagon!
I've been only three days sober and the final straw that pushed my decision was that I got drunk and ruined MY wife's birthday on Sunday so I can empathize with you there, my man.
It sounds like you are feeling like crap right now but, you did make it over 90 days and that is a huge accomplishment. Your girlfriend should be proud of that and hopefully recognize that you are not perfect and you simply slipped up.
Don't forget, time heals all wounds. She'll come around.
If you got sober once, I'm confident you can do it again and stick to it this time, now that you have seen the downside of trying to sneak in a few drinks and where that has lead to.
You're gonna make it my man!
jack