I Have No Idea Whats Going On

There's this guy I used too like who would always pick on me and talk to me, seriously like every day. He never calls me by my actual name he always calls me this nickname he made up. He was always like laughing and joking with me, he was always trying to make me laugh. There for a while I kind of thought he liked me but after Christmas break he didn't talk to me for like two months. So I just assumed he didn't like me. Now he's talking to me again, but not every day. We always make eye contact too. I'll be walking down the hall and look up and he's looking at me. Whenever I see him my chest tightens and I feel like weird I don't really know how to explain it. We have never texted or anything like that, but we have always talked at school. But I just really don't understand why he's talking to me again. Did he not like me before? And why is he still talking to me? I'm not experienced with guys so I don't really know how to interpret this.
I do know I could talk to him first, but i'm painfully awkward and guys don't generally like me so I don't have any confidence when the opportunity presents itself. But that is something i'm trying to work on.