I feel for you. That sucks to be in your state of mind right now. We have all been there and it’s hard to focus on much else when you feel the person you love is slipping away. Basically there are a couple things that come to mind that might help.
First, communication is essential. Tell him exactly how you feel and if he brushes it off, that tells you a lot of what you need to know. If he doesn’t listen to you while you are in pain, unfortunately he probably is not the guy for you. That’s a tough pill to swallow, but it’s a lot tougher if you find out after you commit more time. If he does listen however, and I hope he does, and makes an effort to ease your heart’s pain, then you have something there, and you can ignore the next part.
Second, is perspective. You can’t have it because you are in the thick of it. But trust me, I know where you are right now. Second guessing each interaction and wondering “what the fuck?”, “did I make it all up?”. If he isn’t the guy for you, a clear mind and emotional-removed hindsight will show you there were signs already, and you will realize that you better off seeking someone else.
Everyone deserves to be wanted; if he doesn’t want you the way you need, then you shouldn’t want him back. Relationships are about reciprocated feelings. Find your inner strength. Recognize you will be fine without him.
Then talk to him and hopefully you guys get back what you had. Go in with a level head. Nobody wants to feel like shit, even him, for his neglect, so don’t burden him with him with guilt, but state your case and if he is genuinely in love with you, he will receive it the way he should.