Trust is really an active thing, it's very much based on what you do with your experiences. Thing is, if you, right now focus all your attention on what has happened to you but people in the past, you're basing your trust on a more global scale, in other words you're saying you can't trust him because OTHER people are cheaters. I know this is easier to say than it is to put into practice but here's what I do. Think in the now, the current relationship. Dont' even focus on it in a negative way looking for why you shouldn't distrust him, how he HASN'T cheated, how HASN'T lied to you etc. Instead focus on what he'd doing. He's always there, or he's always been honest with you etc... In a way you shift your beliefs about someone. So coming from the belief that he's good, he's faithful and true, you look for things that will strengthen that belief. Over time, this will grow and it will become second nature. So when you start from thinking about how trustworthy he is, you'll notice how he always tells you where he's going, for example and each time he does you're remided of this. I've heard this described as putting legs under the table, which is your belief. The more things you find to support this idea, the more legs, and teh stronger your belief, and in this case your trust will become.

I know I've rambled a bit but I hope this makes sense and helps.

And congrats on finding someone worth doing this for! *hugs*