boyfriends....

So my boyfriend and are taking a break because I just can't deal with it right now, by it I mean not feeling as loved or cared about from him like I used too, or respected. It was putting a huge toll on both of us. So we're taking a break. The longer it goes the more I think about my past relationships and the happy times. I feel like I'm cheating when I do that. I told my boyfriend about it and he said maybe my having depression is making it harder to be loyal. Thoughts?