Woah. Well, at least you have sorted out your feelings, gotten them all out and really know where your heart. I commend you for going here and getting it ALL out.
I do believe that she was hurt, probably deeply, by your "drunken" actions with those other females. That isn't something that is easy for a girl to forget, or forgive. Maybe that pushed her into thinking about the relationship and how strong or true it is. As you said, it's a long relationship, and you feel as though she is your "soul-mate" but you must be honest that if she doesn't love you as you have once loved her, it is over. And sometimes, "just being best friends" is painful, angonizing and impossible. One expects one thing, the other gets annoyed or jealous.
Though, I know how you feel, regarding the texting and constant contacting or wanting to call her, it does seem to push some people further away. When you step back and show her that you can live without her (even for a day) then maybe she will see you stronger and more mature and will respect that, come back to you honestly.
I understand how hard all of this must be for you. You really shouldn't have fooled around or kissed others, if you did indeed find your life-match. But, I'm not one to say how one should act.
Try not to drink too much, aye? It seems when there is alcohol around, trouble is a few steps away.
Talk to her, but don't bombard her with emails and phone calls. Don't stalk, though some may seem this to be oddly romantic, most find this to be psychotic.
Stay int ouch, give her space, tell her how you feel and wait.
See what happens. If it was meant to be, she will be in your arms in no time. Maybe this singer-infatuation she has is just a girlish passing thing, and could have something to do with the fact that you weren't all that faithful in the past? I'm glad you know that what you did was wrong.
Good luck, be honest, keep your distance but don't give up.