The same thing happened to me, my girl was acting strange and at first she would deny that she was talking to any one and if her cell rang she would tell me it was her mom. I am a very blunt and "strong willed" person so I was very forward and ask her if she was cheating or thinking about cheating and being in love I bought it until one night she told me she was going to her dad's,I have never felt anything as strong as the feelings I had that night. The next day I called her and we talked she ask me to go out and eat but still feeling that she was hiding something I said no, while I was still on the phone with her a friend sent me message via yahoo saying "your girls cheating here is the name of the guy ((kyle)) when I ask her she said yes I cheated and no I dont love you anymore, that was the worst day of my life, a few days later she came to see me at work, she cryed and said that she did love me and I took her back, we have been together for 2 years now and every day is a battle I wont lie its hard but if you love her show her and you can make it work. but still I hope that she is telling you the truth and you do not have to go threw what I did