Both of you are very young, and maybe he just wants some freedom. While there are some first-love type relationships that last, most of them do not. People are different when it comes to commitment. Some are thrilled to spend their life with the first person who really makes them happy. Others need to explore their own preferences by meeting different people. They feel as though they might be missing something if they just settle down with the first person they fall in love with.
On the other hand, decent guys really do not like to hurt girls' feelings, so he might be willing to talk. Tell him that you need for him to level with you - that you are already hurting, and what he has to say will not make it worse.
I know how much it hurts right now; and it will hurt for awhile. But waiting around for him or hoping that if you try to just be friends for awhile he will change his mind will only prolong the hurt and delay the healing. You sound like a sweet person, and I have no doubt that you will meet someone else