Is it normal that my ex randomly contacts me every few months then ignores me?

Ok, so a few months ago I got involved with this guy who really treated me like shit. It was my first relationship and i didnt know any better. During that time he was really controlling and verbally abusive. It only lasted about a month, but the whole thing was really disturbing and snowballed into a lot of other aspects of both our lives, to the point were by the time it ended I had developed something of an eating disorder. He was needlesly cruel when he ended it, and honestly the whole thing had left me really shook and messed up.

A while later I saw him again, and in theory in a very brief conversation I forgave him, but obviously had no desire to ever interact with him again. But now, and this has happened maybe five or six times since july, he randomly remembers I exist at 3am, saying hi or something to strike conversation. Im asleep, and dont anwser. But sometimes in the morning I get curious, and when I text him back he ignores me.

Last night he tried to add me on facebook. I stupidly accepted though I knew it was a bad idea, again because I wanted to know why the request. Its not like he paid me any attention when we were together. He even told me, the last time we were together, never to approach him again, though even then I had no desire to do so, and he isnt even telling me why the sudden change in mentality. Once more, he's the one doing the contacting but again is ignoring me. I dont want to get back together, because I think that nothing could be worse for my mental health and really dont want the drama in my life. Like I said, the whole thing was messed up , and I actually lost about 30 pounds since this february; on the bright side I'm an american size two.

I just want to know, is he enjoying messing with my head? Does he just remember me when he's drunk or something, hence the 3am wake ups? I didnt mention this before but I vaguely know he does have a personality disorder, so is that it? Because one way or another this feels like torture, and brings back painfull memories.