What should I do?

My boyfriend and I have been together for almost 2 years now. He proposed to me a few months ago. Our relationship started out really close, but then he moved and we then were in a long distance relationship. He has a history of cheating on me and I've gotten over it. The problem is he's done it again. Its understandable considering we're in spate states. I'm not perfect either. I just wish he could be honest with me. He's in military school and the only way we can talk is through mail. I was wondering if I should bring up my concerns to him or just be his supportive girlfriend.