Relationship Advice...please?

I've been dating my boyfriend for a little over 2 and a half years. When he's on his A game, he is pretty much all I could ask for in a boyfriend. We've had our problems like anyone else and we argue from time to time, but for the most part we have a very loving, open, and honest relationship. We have the type of relationship where we can speak frankly and openly with one another. Its something that I really cherish about us. I should mention we currently live together (I'm 24, he's 22 and a half) but are at very different life stages. He's about to finish up his undergraduate degree and I've been working full time in a professional field for almost 2 years. (We meet when I was still an undergrad) Now here's the actual problem or concern. He told me about two weeks ago that he's not sure if he wants to continue dating long term. But he doesn't want to break up, he just isn't sure right now. I keep telling myself its because he's about to have a lot of huge life changes happen (moving out of state away from everyone and starting his first full time professional job). He'll also be living on his own for the first time. But now, I'm not sure. He seems to be distancing himself from me but I'm not sure if that's related to his unsureness or due to finals coming up. I just feel really rejected right now and like I'm in limbo waiting for him to decide that he wants to be with me. About a 8 months ago he was professing his undying love for me and even gave me a budget to go look at engagement rings...and now we're here. He says he wants to keep working on us and to hopefully rekindle the pion we once had for each other. But I'm afraid he's just biding time to gather enough strength to let me go gently. I'm just really confused and hurt and thought maybe someone else could make some sense of this. Sorry so long. I should also note that he says he isn't interested in dating anyone else and he promised me that if he did he would end things with me first before going behind my back. And I believe him on that, so it's not that there is someone else. Any thoughts or advice would be greatly appreciated.