Why isnt he talking to me?????????

There is this guy I really like and I have every single cl (Periods 1 through7) with him and in computer cl he talks to me alot and is very funny and we flirt. He wont talk to me unless we are sitting right next to each other. In social studies he wont talk to me unless we have group work and sit by each other and in science we are microscope partners and he doesnt say a word. science and social studies and period one and two, is he like tired and craby or somthing, what is wrong with him?