Is THINKING of leaving the same as wanting to leave?

I've been in a 3-year relationship and from time to time I have thoughts of leaving my boyfriend for somebody else. I have had a few crushes during our 3 years together that I haven't acted on but have still had thoughts and desires about. For instance, I traveled abroad and met a guy in my travel group who I felt feelings for but I never made a move on him. To this day, though, I still think about that guy, wondering if he still thinks about me. I also sometimes think about my ex-boyfriend and how much I loved him (but I'm over him now) and all of these thoughts make me feel really guilty. The current boyfriend and I have a decent relationship. We have trust issues because of said crush abroad whom I confessed about. When I'm not thinking about somebody else, I really love my current boyfriend and I love being with him. I only occasionally think of being somebody else's girlfriend... no more than once every 2-3 months. Are these thoughts normal in a relationship? Should I not be with my boyfriend if I have these thoughts? Is it wrong of me to have these kinds of thoughts in my head?