Long distance relationship

Since I was in about 3rd grade I've had really bad anxiety.... Especially about losing people I care about. Well, recently my boyfriend of 3 years (who is my very best friend) moved away to play college baseball. He made that decision by himself and without really asking me if I would be ok without him (even though I'm glad he's pursuing his dreams it would've been nice if we would've gotten to talk about it first). Since he's moved away my anxiety has really flared up. I worry incessantly about something happened to him while he's away, or him finding someone else while he's up there, or us growing apart. I know every relationship is different but I've heard of so many relationships ending because they become long distance. 4 years is a long time to live in different cities. Plus, because of his practice schedule and my work/school schedule we don't have a whole lot of free time to see each other. I know a lot of people go through this when they start college and I'm trying to think logically about it, but I'm having a hard time getting over my emotions. It's not just that I miss him, I'm always worrying that I'm going to lose him. And I keep having panic attacks thinking about how far away he is and how little time we have together when we do get to see each other. I hate to be a clingy, possessive gf so I'm trying not to worry him too much but sometimes it feels like all of this is too much for me to handle by myself. That's why I'm posting to ask you guys for advice. Thanks!