Am I Overreacting? My Long Distance Boyfriend Seems Distant

I find myself becoming insecure in my relationship and I’m unsure as to why… In the past I haven’t really had a healthy relationship and eventually something would come up that would begin to make me feel insecure like they intentionally grew distant or they would talk about me behind my back to others (silly examples but alas). But right now I’m in the best relationship I’ve ever been in with my current boyfriend! We’ve been officially dating for close to 4 months, but talking for longer. He’s nice and funny and respectful of both me and other people… we have never really gotten into a “fight”, and anytime we have a disagreement we are able to find a middle ground pretty easily. Recently though he moved out of state to go to school… and he isn’t really that far (about 4 or 5 hours) but it’s still been a little bit rough - for me at least. I’ve done long distance in the past, and I’ve managed to make things last for years with people I’ve never even met in person/got to see. With him even though we see less of each other we still get to meet up! So it’s not destroying me… but it is upsetting me and I’ve begun to convince myself that I’m the only one affected by it. Things were going pretty good for a while - we would call and talk everyday and send voice messages and pictures! And just recently I flew to him to visit for a week, and we had lots of fun!!! But towards the end of the visit I got this impression that he was growing tired of me… and when we got to the airport for me to go home he didn’t see as devastated as I did. When he left for school initially he wasn’t as upset in person but he messaged me later about how sad he was… this time he didn’t. It’s been about a week since then and he’s just seemed a little bit distant. He usually responds in a timely manner but now it’s taking him hours to get back to me… and when we do talk I feel as though he is less interested in what I have to say now. He’s told me that he’s really busy with school, which I do believe. He has to read A LOT for his classes, and I wanna say that that’s the only issue but my mind is constantly looking for a reason that he might not like me anymore. We both have discussed that we enjoy and prefer words of affirmation as our main form of affection especially since we are now long distance… and I don’t feel like I’ve been getting that from him lately. I’ve been thinking back on my past relationships and how people who grew tired of me would slowly begin to respond less and less and I would find myself talking more and more to fill the silence… and I’m doing that again now. I also find myself wanting to revert back to old unhealthy behaviors… like maybe if I drew back and texted him less he would show he missed me more or something stupid like that and I hate it! I sort of feel like it’s a “if I never said I miss you first, would you tell me you missed me?” type thing. I have a history of anxious attachment styles taking form in my relationships. I don’t wanna fall back on old habits but it’s making me so anxious and I don’t know what to do!! Am I holding someone to unrealistic standards? Am I overreacting and maybe he truly is just busy and doesn’t have the time? How should I go about bringing this up in a way that doesn’t make me come off as super needy but still expresses my concern in a healthy way? I know communication is key and I want to be able to communicate how I feel but I don’t want to come off like he’s my lifeline and everytime he makes a change I’m going to freak out! I love him a lot and don’t want to lose him but I’m worried I will and fear my mind is constantly trying to ruin this for me… how can I just enjoy it for what it is? TLDR: I (19F) am starting to think my boyfriend (20M) is losing interest in me. We recently went long distance and after a short visit to him he’s been less affectionate. I want to ask him about it, but I don’t want to come off as needy. Am I overreacting? How should I bring this up to him?