Boyfriend drama

Help IDK what to do. Something happened to my bf last week and it seemed really serious I asked him what happened and he said oh don't worry I'm fine I don't really want to talk about it and this was not last Saturday but the one before that. And before that we were like so close and everything would text all the time when not at school and Skype most nights but when he told me something happened he didn't text me all Saturday or Sunday and I told him to text me when he wasn't busy but he didn't which wasn't normal and then last Monday when we went back to school I thought I would talk to him then but he was sick for the entire week and we barley talked I contacted him once and he basically said straight away I have to go I will ttyl and I was getting worried so I asked if everything was OK between us and he said more or less and I asked what does that mean and he said idk and then said sorry I have to go I will ttyl. So I was freaking out and he came back to school on Monday and it was so weird usually we are all close and holding hands and hugging and stuff but I could tell he was avoiding me and something is still up I know I have to ask him about it but ifk what to say or how to do it and I'm really worried what should I do? Ps sorry it's so long and thanks to all those people who actually read this