I hate this topic but I believe it's my duty comment on it...
I was in the same boat as you but I think I have it worse than you. I was with this girl for 8 years since I was 15 years old in high school. We were each others 1st in every sexual aspect imaginable. We won our high school's cutiest couple superlative. Everyone wondered when we were going to get married.
We went to Junior college together, did everything and anything...went on trips to Islands, Florida, you name it we did it. Both tied at the hip

Her father went to jail for Real Estate Fraud and I helped take of her family w/ money and mental support. Her family loved me, her parents/siblings said they couldn't wait till we got married.
Her dream as a little girl was to go to NYC to become a dancer/singer, so after Junior college she left for a 4 year college in NYC to get her BA in Dance/Theatre and then after that, start her adventure to be a successful dancer/singer.
She didnt want to leave me but I was only 50 miles away from where I lived to NYC so it was only little 45min drive. The 1st 2 years she commuted back and forth from NYC to our hometown so I saw her every night when she got back from school. That was great and plus her not being attached at my hip 24/7 was also good for us both, because it made us want to see each other that much more.
After the 2 years she recieved her BA at in Dance/Theatre, and everything was great.....Sex was great, communication was great, we knew that we would be with each other forever. This year 2006, she insisted that she wanted to try and live in NYC for 1 year to see if she could conquer her dream as a professional dancer/singer. Shame on me if I didnt let her live out her dream. What kind of BF would I be if I wouldnt let her do what shes been to dieing to do? She wanted me to live there with her but I'm not a city guy, plus I had just started my career in our hometown. I lent her $2000 to put down on an nice apartment on the upper east side with a girl that she knew from her college. I helped her move, bought her a laptop, a $700 mattress, new odds and ends for her new apartment. I went to visit her every weekend to site see Manhattan and to of course be with her. But then all of a sudden the SEX went bad. I'd figure that she would be all over me since we only saw eack other on the weekends, but that just wasn't the case. She said it wasn't me and that she was stressed out with money and the living conditions. I agreed that $400 a week as a hostess wasnt going to cut a $1900 month rent, plus other daily expenses. I brushed it off and continued to love her as promised, even though were only having sex 2x a month.
Well, time went on and I began to get very suspicous over her phone bills being very high. Her bill was under my name so I always could find out who and when she was making calls. I never did this before, but I had a hunch to see who she's been talking to. A city number that she was calling 20x a day kept showing up...I called it to see who it was

It was a guy at her work that she was with for the last 8 months.

I spoke with the guy and she was playing him like she was to me. If a girl is going to cheat on me it better be with a RICH Justin Timberlake looking mutha fucka. This guy was an ugly piece of shit waiter who worked with her. He thought he had a ligitiment girlfriend for the last 8 months, so he felt it was his duty to tell me everything. He explained that even before him, that she dated his friends from work 2 years ago. What's strange is that she once introduced me to this guy when I went to visit her at her restaurant a while back. I guess she told him I was a friend from school or something. Sneaky bitch!!!
So all in all, this girl who I thought was my soul mate, has been cheating on me for the last 3 years with multiple guys, and I never cheated on her.
I thought that if I couldnt trust this girl, how the hell could I trust another one?
If you're having doubts on whether you think you're girl is cheating on you...some how get "her" cell phone bill and call the number that keeps popping up on the bill. Remember she is innocent till proven guilty. So do your investigation!!!!
This is very new to me only 2 weeks ago I found all this out.