How do I trust the guy I'm w/?

We started seeing each other about a month ago & he tells me he likes/loves me & wants to be w/ me, but seems secretive about some things. He professes his feeling for me on his myspace & tells me if old female friends contact him, but lately hes been wanting to stay home more & more. He talks about his exs alot & i always thought you talk about the ones you miss. It seems we cant have a conversation w/o him bringing up someone. Whether they were just a friend or more. He kids around alot so its hard to tell sometimes if hes joking or serious about his past. I tell him alot of it I don't want to know. I believe its not an issue unless its affecting our current relationship. He knew from when we started going out I had trust issues & that I havent had the best role models when it came to love. But now he says they are a problem for him. um i dunno. Any advice?