dude I know how you feel. I was caught drinking four times before i turned 16 (once by my school). it fucking sucks everytime your like fuck im not gonna do this again or im just gonna take it easy for a while. It will get a lot better. the first week or so are awful but it gets better quick. your parents will forgive you just keep everything else good, your grades, ect. and also act like your wicked sorry even if you arent. every time i got caught I acted like a pusys to my parents, saying like "I dont know what I was thinking and im really sorry because I know i betrayed your trust (again), blah blah blah"
but thats wicked gay of your girlfriend to text you that especially because she didn't know the story. and im sure she was just scared/pissed off that she got caught, but shes not worth your time, seriously, forget her.