Indecisive

I've just finished my year two exams and they've been really tough, especially the fact that I've hardly been able to speak to my girlfriend of now 4 months. I do feel as though the spark has gone out of our relationship alittle and we do find it very hard to talk, and I often feel like she doesn't want to talk, but I don't know whether this is just due to the exams.

Well here's my problem, when we first got together I had another very close friend who I had also toyed with asking out. Through the exam period we have laughed and talked way more than I have with my girlfriend and it also feels more natural. Well my girlfriend went away this weekend and me and my friends including this other girl went out, and there was alittle alcohol involved. Well we sat alone and just talked for ages which led to a kiss. But now I feel so incredibly mixed up and guilty, but I just don't know what to do, please help. Please don't jump to the conclusion that I am a total bumhole, this is really upsetting me, and things have been so hard for the past few months, I just don't have a clue what to do anymore.