How do I detach myself from him? Please read?

Me and my neighbor kinda dated for 2 months. We both left for the holidays and while I'm back, he still hasn't. The first week we were apart we texted almost every day, he even called me on Christmas day, but the conversation was nothing special, just normal stuff like what are you doing and so on. I've noticed he's been acting weird in the last 5 days or so, in particular I noticed it on Saturday when I called him at 10 pm and after a while it seemed like he had ended the call. He then texted me 2 hours later around midnight asking me how I was and when I told him about the phone call he said his phone hadn't rang at all. Didn't hear from him on New Year's Eve, i wished him happy new year on Monday as soon as I woke up and he replied 12 hours later. When I asked him what he had done the night before he said he drank a lot. He didnt't ask about me, my day, nothing. I haven't heard from him since. I feel like he doesn't deserve me at all, I constantly think he's cheating, he shows no interest, I'm just tired. At the same time though I'm scared things between us will end, and it will be difficult to deal with it since we live next door. What do you think? The ugly truth is that I can disappear and go no contact with him and he still won't care or notice.
How do I detach myself from him? Please read?
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