Thanks to you, I now have REO Speedwagon stuck in my head. Not necessarily a complaint, I guess.
Good for you. I don't say that to be sarcastic or to offer trite condolences, I mean it. You obviously recognise you made a big mistake (or several, if we're counting), but taking responsiblity for them is a big step. Your girlfriend may take you back, maybe she won't, but you'll come away from this with a greater understanding of worth and I think that, even if you can't use it right now, that'll be a good life lesson for you.
I think you have an over-romanticised view of love. Are you saying because he had a moment of infidelity that he cannot possibly love this girl? Seems to me that his was a fairly natural reaction after having some drunken escapade flung upon him in the cold light of day. With hindsight we can look at it and say, "yes, he could have handled that better", but I doubt any of us would have had that clarity at the time.
Maybe it's easy for me to say that though, since I have trouble getting any girl to give me the time of day
I will say this, though; trust isn't something that generally breaks down completely over a transgression. It is cracked, and damaged, and whatever else, but there is no reason it can't be repaired, even if it takes time. Not knowing you, Dark__Knight, but I hope if you're as sincere as you seem that you get that chance.