2 relationship questions! Please Help!!?

Me and my boyfriend are very open and know alot about eachothers past relationships and history. He told me that sometimes when he is in the mood that he thinks about past experiences. He said not the women themselves, but what happened (like making a movie or a place) and how it was nice and maybe i'll want to do that with him or how he wants that experience with me. He says he doesnt think about the other women or compare me to them or wish i would do something something they did. Just what he liked in the experience that he might want to happen again.

It kinda bothered me because honestly I only want him to think about us and for the most part he says that is whats replaying in his mind. Should I be worried? Or is this normal for him to have those thoughts?

Also, I've been very hurt in the past. Cheated on and lied to, even by my sons father when I was still pregnant. So at times I'm very paranoid about him cheating or finding someone new. We've been good friends the past 2 yrs, dating 9 months, and together almost 6 months, and associates for 4 yrs. He thinks if I keep positive thoughts things will keep looking up for us, and bearing negative thoughts vice versa. But he's very good to me and my son (13 months old). Brings us around his family, says he wants to work to marriage, calls my son his and treats him that way. Says he loves us, and Im the best woman he's been with and he'll never cheat because he's been cheated on and knows how it hurts. How can I stop being so paranoid? Im afraid of bringing bad karma onto our relationship and something bad end up happening.. Help!