What is wrong?

My boyfriend is a really good guy to me and shows me that he loves me every chance he gets, he gives me attention as much as possible, takes me out the house, comforts me, etc. but for some reason I still think sometimes things are just going to go up in flames for some reason...I don't think I am a bad girlfriend, and like i said, he's a good boyfriend. I can usually talk myself down and be able to calm down my random thoughts of it all ending by using logic and examples of how he treats me because actions speak louder than words. But will I ever "grow out" of thinking it will end?

P.S. I sometimes get the thoughts when we have heated discussions or I feel like he's ignoring me or holding out on something. But sometimes there's no clear reason to me and they just pop up. I have had 3 past relationships that ended badly so maybe that is why I think this way sometimes.