Why is my ex boyfriend hiding his feelings from me?

My ex boyfriend didn't wish me on my birthday. Could it mean he doesn't care anymore or is he just too shy to admit he still have feeling for me?I know he still likes me because it's very obvious and my friends feel it too. I wish him happy birthday true fb last feb but he didn't reply. At that time, I went oversea and he knew about it as I put it on fb. When I came back, it seems like he missed me a lot because he changed a lot. He was all nice and sweet to me and trying to be close with me again. But I get so hurt when he didn't even acknowledge my birthday. Could he be hiding his feelings? He is a very shy and private guy. He wouldn't even tell his friends about his feelings.