What is causing him to act this way?

We've been dating over 5 months. He's 16, I'm 15, we're both sopres. We didn't see each other at all Christmas break, but he called me a few times. I missed some of his calls, and when I called back he sounded happy to see me. But ever since school started he's been acting so distant! And that time I called him was New Year's Day, so it wasn't that far away from school. My best friend noticed the way he was acting and told him she did. I didn't go to school last Monday cuz of bronchitis. That night he called me and asked why I wasn't at school. He also said sorry if it seemed like he was ignoring me, and that he just needed help with cles he was having a hard time in. But we haven't held hands for about a month! He's making me feel like we're just friends, and that hurts me sooo much! This week, on Monday, he was at school in the morning and said hi to me, but then wasn't there the rest of the day. He wasn't there Tuesday either. Today I saw him in the morning and he said hi to me again. This week is final exams. He got one of those slips that you can leave the school for lunch, but I didn't, and he just left with his friends. Then he didn't even wait for me when he left to go on the bus that takes us to our buses (hope that's not too confusing). My friend and I went on that bus (we didn't even know he was on that one) and so we sat by him. All he did was read a book. He didn't even say hi to me! When she asked what he was reading, he said "None of your f*cking business" and he sounded really annoyed. The only other thing he said to me was asking how I did on my exams. Then he gave me a hug, but a really quick one, and that's not what he usually does AT ALL. I really really don't want to break up with him! He has told me he loves me (not that recently, but he has said it). Breaking up is THE LAST thing I want to do. I would call him, but he is probably busy studying for exams. HELP! All answers appreciated! Sorry about the long question!