Boy problems, we've been dating for almost 6 months and we're distant since summer started. Any advice?

I need help. We're both 16 and have been going out for 5 months and 2 and a half weeks. I know I love him and I thought I knew that he loved me.. before summer started we were perfectly fine and now that its already a few weeks into it, he's acting so much different. We haven't gotten to sex and we don't really plan to until later. We don't see each other that much because his mother is lazy and when I try to talk to him about our problems, he always gets upset and trys to change the subject or just stops talking to me. We're always arguing about different things and he seems to be getting more jealous now. I really need advice, why do you think he's doing this? :/Boy problems, we've been dating for almost 6 months and we're distant since summer started. Any advice?
sorry to say this but everytime I was in a relationship with someone and it all of the sudden got distant, they broke up with me due to ';needing more me time, and its not you its me';