Flirting Hits, or Abusive Hits?

I use to think he liked me, I mean he started us talking on Myspace and we did that for a week. Then at school we'd playfully flirt and before all of this I would catch him looking at me. Once he just walked up to me and hugged me. Then he came up behind me and put his arm around me and we walked to his cl. We've hung out 3 times, once where he paid for our lunch and gave me a hug at the end. He's come by my workplace twice now and we just started talking about a month ago. We would text almost everyday but now it's a little sparse. He'll hit me in my leg sometimes and he did this before but now it seems different. I overheard his friends say he gets serious too much and slammed this guy into a wall for no reason. He'll still do nice flirty things and the hits aren't enough to cause damage but why is he doing it more now? It makes me think he doesn't like me anymore, we're both in high school. Is his "hitting" flirting or abuse?