boyfriend

I've been cheated on by all three of the boyfriends I have had. I was single two years and now I'm dating my current boyfriend. I love him and he's great, but I can tell I don't let us get very far because I'm afraid he will cheat and j overreact. He has never made me believe he would cheat. It's just my past experiences. What should I do to help myself help our relationship? I'm desperate.