Why is he acting like this?

right ive been friends with this boy since secondary school and weve left now to go to college and i spoke to him on msn saying im scared because i might have diabetes :S and then he was saying theres nothing to be scared about. Then i said i dont know if i will die from it but its a possibility and then he said "yeah well dnt tell me the possiblilty u just want me to feel sorry, i dnt like that" and then i wrote something back to him and he hasent replied back since :/ whys he acting like this, it just feels like he dont even care if i died or not :/ and i dont talk much to him cause im shy around him and i like him and he knows i like him but he gets annoyed wen i dont talk to him. And i went to his sisters party last saturday and i hardly spoke to him and he looked a bit annoyed but i dont know if thats why hes mad at me? argh im just so depressed atm :/ x