should I just leave

Me and my boy have been together for 7 months now and I'm his first everything, the first couple of months were AMAZING I could complain, however things have really gone to shit. He avoids coming to school for I dunno what reasons, he doesn't speak to me for days and then when he does he wants something from me, he doesn't want to come round or go out and do something and I've told him how I feel about this but hasn't got through to him. Even tho we are quite young but old enough to have sex (which we have) it just breaks my heart that I feel like I'm losing him and I dunno how or why ?? Someone please help x