How do I get a pword for Myspace or Gmail?

I am pretty sure that my bf of 4 years and father of my children is cheating on me either on Myspace or his email. He says that he has nothing to hide, but won't show them to me to prove it. I had found somethings on the computer for an Eros.com that said something about searches for transuals and also on craigslist personals and other things also, which is disgusting. I would like to know the truth but I am obviously not going to get it from him. Is there any way I can retrieve the pwords for Gmail or Myspace. I have tried the secret questions on Gmail and everything but cannot figure out the answer. Is there anyway that I can pay to get it?