need help/advice, My b/f says he is not cheating but is the writing on the wall? Please

[confused]

PLEASE help!???!!? My b/f who I have been with for 3 months and I have known him for 2 years. He moved in with me about 2 months ago. He is 24 and plays in a band he is really good and does well for himself. I am a working mom. He stays home during most days while I am at work. But here is where it gets odd. last month I was cleaning out my car and I found cocain in my car I asked him if he knew anything about it and he said no, so I let it go. Last week I came home and I found a girls purse out on my patio we live on the 2nd floor. The purse was sitting on the chair. I looked through the purse and found condoms panties, federal financial aid papers and banking statements. I never heard of this girl before and my b/f says the same thing. I have asked his friends and talked with his family and they all say he is not cheating on me. I asked him how the purse got there and he said he doesn't know. Could this be the work of 1 of his ex's or 1 of mine? My 9 year old daughter adores my b/f. Please am I being nieve? Or could this purse have been thrown up on my balcony? All attempts in trying to find this girl have failed. What would you do?