Guy's Behavior

Does he like me, or is it just to mess with me?

So I met this guy a month ago and we met because he wanted to know a embarassing story of mine (teacher went through my bag). At first he nagged me to tell him over and over again. It involved one of his teachers so he obviously wanted to know. I told him I don't want to tell him. We sit at the same table, so for the first week he would just constantly ask. But over time he began stealing my stuff like my Pencils. It's like a fun game he does where he has to steal it without me knowing. He gives it back once I see he take it. I personally don't mind that he does this because it makes class more fun. Today I asked why he takes my Pencils, and he said "because it's just fun". He talks to me all the time and whenever he sees me he yells out my name. We walk back from class together, and he spends the entire time asking about the story. I don't know if he is talking to me and walking back from class with me because he wants to know the story, or he wants to be my friend. I have no idea why he wants to know so bad. Also... he has a girlfriend. So I thinks it's very weird that he does all this stuff. Can someone PLEASE explain what's going on. I can't tell if he likes me and shows it by taking my stuff or if it's all because of a stupid story.

Updates
+1 y
Ok. Today I asked him why he wants to know about the story and he said "Bc I just want to know about it". Same thing tho. Yelled out my name every time he saw me. It's so weird, bc he NEVER mentions his girlfriend. Over the year I've never even seen him talk to a girl.
Does he like me, or is it just to mess with me?
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