Girls, how do you deal with this with your boyfriends?

i'm in a relationship for almost 10 months now with somebody i love very much and whom is also quite in love with me as well. i never had a boyfriend as i didn't care for one before but my boyfriend did date a bit. not too much, he is 27 and told me he only slept with 3 girls. since then, (since he said that) i couldn't stop yzing things in my head. ex experiences, experiences, just the curiosity is killing me to the point that we even had some arguments over it and i got into tears over yzing things about it. i am not a jealous person but recently i even snooped (i know i know) on his computer in his pictures to see if he kept anything from his exes. i saw nothing. i went into his doents and found transcripts of chats with past flings, etc etc. i'm sure it's accidental but still!!! i'm not a jealous b-tch guys. i'm actually a philosophy major going into an MA programme so please don't tell me i'm some little whiny ditz. i have a problem so how do i solve it and CEASE this "boyfriend's past'' nightmare??? how do i stop creating scenarios in my head that he keeping secrets, cheating, lying, or did some promiscuous things, etc. please help me change my thoughts because i have suffered tremendously with this over the past many months. many thanks, A+