well... i can't say anything about getting the pair of you back together but i will say this: in future, don't hide stuff from your gf if it's gonna make her paranoid about it being her fault. if something's screwing around with your personal life, you should tell her and i'm sure she'll be supportive to either 1) help you through it or 2) let you some room to think...
and remember: i'll never be able to figure this one out but girls have a 6th sense i don't know how but they just do... they'll always sense when something's wrong especially if something's wrong with their bfs
hmmm actually i can say something trying to get the two of you back together, tell her about what happened? i derno if anyone's already said it but i think apologies have become overrated as well... sure you can't say anything more than 'i'm sorry' but at least show her why you're sorry... if it was me, i'd try to get her alone and just say: 'hey... you remember the other day when i went off at you? well... some stuff happened during that day and i thought you just might like to know..."
hey hey... you finish this off, i think i've given you enough to begin with
good luck dude