SUBREDDIT: r/relationships
TITLE: Want to know if I [21M] have a shot at fixing my relationship with my girlfriend [22F]
POST: I know it's a dumb overasked question but I just wanted a couple candid responses. 

So this starts over a year ago. Me and my girlfriend had only been dating for a couple weeks and I was uncertain about how serious I was about it. I end up going to a very ratchet house party and I get very drunk and start dancing with this girl. We make out a little (terrible I know) and then I go home with my friends after we exchange numbers (again, yes, terrible). We text back and forth for a day and she tells me to come over. Me being dumb and horny I agree (I am the worst). We fool around on the couch, but when it comes down to doing the deed, I have a mental freakout. I decide I want to get serious about my girlfriend, so I get the hell out and I don't text her again.

Fast forward to several days ago. I have a separate different female friend who I used to hang out with a lot, but it made my girlfriend uncomfortable so I stopped. She texts me asking if i want to go to her house for a party which I agree to. I did not tell my girlfriend. She finds out and gets angry, but we make up and I think things will be OK.

Then the other day she's looking through my phone. Now I had deleted those text messages, but they were over Google voice, so after backing up my phone a while ago they get restored. She reads them. She's devastated because just when she thought she could trust me this happens.

Now she's blocked me on my phone and facebook. I get that she's completely in the right on this, but I also feel like I'm a completely different person than I was a year ago. Think I have a shot at taking me back, or has too much damage been done?
TL;DR: 
I fooled around with a girl when me and my girlfriend first started dating, she finds out a year and a half later, shit unfolds predictably.