<human>: Provide a brief overview of the text.

I (M22) and my girlfriend (F20) split up a week ago due to difficulties with our long distance relationship. We'd been together a year. I really want her back but I found out a few days ago from a friend that a girl and I kissed on a night out back in October. I was drunk and don't remember it, although I thought I remembered the whole night. I'm not sure if she kissed me or if it was the other way round, although the girl does kiss a lot of guys when she is drunk. I feel terrible, I love my ex, and usually told girls trying it on to leave me alone as I have a girlfriend. I feel guilty that I knew nothing about it for the last three months of our relationship. I have never felt anything for the girl I kissed, and I never wanted to hurt my girlfriend. 

I'm at a lose with what to do. If I was to get back with my ex I have no idea how I'd tell her. I've also asked my friend (who is friends with the girl) if she knows what happened to see if I can get a clear idea of what happened.
<bot>: May have cheated on my ex when we were still together, unsure if I'll be able to get back together with her now I've found out.