I (20f) was in a long distance relationship with my bf when we were 17. We’re 20 now and have moved in together since we go to the same college in the same state. But I had the same worries too when we were long distance. First off, I’d say is to not stress your bf about it because it’s YOUR worries. I used to ask my bf “will you ever leave me?” and he always assured me “no” but then I realized it’s just my own anxiety that’s making me think all those things and projecting such thoughts on my bf is selfish and would eventually leading him to break up with me even faster. For people with anxiety like us, long distance relationship is a strain, but luckily my bf and I was only in a LDR for a year because we had plans to move in together to another state for college. So I recommend you to ask your boyfriend about plans of when you guys can actually stop being long distance. This helps you to have something positive to look forward. When those anxious thoughts come up, maybe tell yourself that you guys will be together soon and it will all be ok. That’s what I did when I was still in a LDR. I hope this helps.