Should I leave him alone?

Personally, I would let him to come to you. If you give him enough space he will either realize the following, yes he likes you and still has feelings for you or no it wasn't meant to be. Also if you give him his space this will give him time to miss you. If you bombard him with calls/texts he won't get the opportunity to find what he really enjoying about you. And also too many calls and texts can come desperate.
I think give him some time, maybe a week. Follow up with a text after a week saying something like, hey hope everything is going okay with you? That shows that you care without coming across desperate. I know that word is horrible, but guys don't like needy girls. Find something to keep you occupied like a hobby or call a friend if you need to talk to someone, it's good to vent it out somewhere.

Good luck, and remember the old saying: If you love something, set it free. If it comes back it's yours if it doesn't. Well it was never meant to be!

Well, if you still like him and think you can make it all better then maybe you should try talking to him for the sake of good times. But, if he really doesn't want to talk to you or tries to block you out then I'm sorry but you JUST have to let go. Like you said he doesn't want to be together. I think that you should give the "lets talk" idea one last chance. If he's not open about it. To the hell with him. Just let it go. I mean, the logic is, he breaks up with you, you give the relationship one last try for a mend, and lets say he rejects. There is no way he can blame you for the break up. After all, HE IS the one breaking up in the first place. You are worth so much more and there are plenty of other guys out there and I hope you find the best one!