Don't say that you're not worth caring about...everyone is worth that. I feel it might be best just to move on from this guy. I know that he showed you he cared and made you feel good about yourself but he is kind of not treating you well now by ignoring you(to a degree). I would not contact him because you don't want him to think that you are 'needy'. If he does not want to hang out with you, that's fine, it is not a reflection of you. When you meet him say 'hi' and if he wants to engage in conversation, he will, and if not, leave it at that. Don't think that just because he does not want to hang out with you that you are not worth hanging out with because of course you are. We all want to be like and cared about. Our real friends don't treat us in ways that make us unhappy. I hope this does not sound too harsh.