<human>: Could you distill the essence of the text into 1-3 sentences?

My boyfriend (20) and I (girl, 19) have been together 16 months. We hit it off the day we met and have been dating since a month after that, we're each other's first relationship. Everything is great, emotionally, physically, all of it.

I love him more than anything, he loves me too. We get to see each other every day during the school year but spend Summers and breaks apart (he's from out of state). He takes me on creative, romantic dates and we love just playing video games or throwing around a football. 

Sounds perfect right? Well, I'm afraid he'll leave anyway. At the very beginning every disagreement we had made me start sobbing and freak out thinking he would dump me. He finally sat me down and said that needed to stop, we needed to be able to argue constructively. I worked on it, that passed. I think we fight very well now. But I still go through these spells of insecurity. 

When he's holding me, I think he'd rather go. When he looks into my eyes and tells me he loves me or that he wants to be together a long time, I feel like he's only saying it because he knows I want to hear it. I'm INSANE and I know it. I have talked to him about it, and he told me he feels like I expect him to fix it and that's not fair. He's right, he shouldn't have to fix it when he's already the world's best boyfriend. I told him I need to be able to tell him when I'm upset though, and he said that's fine.

I try to tell myself I'm being stupid. I save sweet texts and stuff from him and when I'm feeling insecure I'll whip them out to attempt to reassure myself. I don't know what triggers my insecurity and when it finally goes away (which it will, for months at a time) I don't know why. Why do I do this to myself? How can I stop?
<bot>: I get insecure and afraid my man will leave me even though he is loving and caring in every way. It goes away for a long time and comes back for no reason.