Well, if the doubts are strong, and you feel real, I would end the relationship sooner than later. Honestly, I'm engaged, but there were times in my relationship that I was questioning similar things, however, they would fade, and there would also be moments that would take place that would completely erase any doubts I had - and that was when I realized I was just being human, and quite frankly, stupid, that those thoughts even entered my mind. Today, I have no doubt that she's the person I will be spending the rest of my life with and raise a family, however, we're men. We're going to have thoughts, we're going to have doubts. It's being able to work through them that will determine if they're real or not. If this is a lingering problem, I would say you're not going to get over it. If it's keeping you from sleeping, then it's a problem. Don't let complacency, and the comforts of a relationship (I know, they can be great) skew your feelings. It's not fair to you, or her...