Holiday Relationship Issues..?

My boyfriend and I recently got back together (We stayed dating for a year after we broke up) and he told me recently that he did not want to try to make us work. We don't fight, and we get along great. In fact, we took a trip out of town and started getting really close to each other...and then, all of a sudden, he started pushing away...is this a subconscious impulse to avoid getting hurt? Or something else? In our first relationship he was wonderful and I didn't appreciate him at all and I am worried he is afraid I might hurt him again if he gets to close. He insists that isn't the problem. We have been together for the better part of three years, but only serious for about one year of that. He has made it clear that he cares about me a lot but he is only 22 and I know that is a hard stage for young men to go through...what should I do to help make everything alright? I'm all out of ideas.