Does anyone else do this?

Sometimes I imagine not being with my boyfriend anymore and him being with someone else and he's happier. I hate it. It hurts so bad. I love him like crazy and obviously the thought of ever losing him kills me. Especially if he has someone else in his arms creating that beautiful smile of his. I even feel jealous when I think about it. I know he is very happy with me, but sometimes I worry that he could be happier. Is there a way to stop thinking like this or do you guys think like this too? I don't think about it a lot but it crosses my mind every once in a while.