Gave a "nice guy" my number, now he's being very aggressive and it scares me

One of my coursemates in the year below me (whom I don't know very well) got with me at a party last week, we were both very drunk but I ended up giving him my number though I didn't want to go home with him as he was really pushy and a bit too touchy-feely. I'm quite tall and athletic, and he's really skinny and not much taller than me, but I still felt a bit threatened, and he started sulking after I told him insistently I wasn't going back to his despite his assurances "nothing would happen if I didn't want it to." The day after he texted me asking me out, but I said no, as although he's cute and well-dressed and is pretty smart I didn't like the way he acted when drunk. I asked if we could just be friends and he said OK, though I saw him at another party on Tuesday and he kept staring at me and wouldn't talk to me, but he kept following me around. For example, we were queueing for food and I glanced over my shoulder and he was right behind my friend who was next to me, though he'd been at the back of the queue a few minutes ago. I was alone in the living room taking a call from my mum and he spent ages (as in, around 5 minutes) getting a drink from the table next to me. We were out for drinks with some other coursemates after a seminar yesterday (we both do one of the same modules) and he was late as he had to get some money from the cash machine. He had to squeeze past me and everyone else, tapped me (and only me) on the shoulder really hard and was like "Can you please MOVE?" in a really rude tone of voice. I said hi when he sat down but he wouldn't even reply, turned away from me and was obviously ignoring me for the rest of the whole time. He's now texted me asking me if I want to do a presentation for the module with him (we each have to do one in a pair next week), obviously I've said no. Have spoken to mutual friends and they said that I was being a bit bitchy for turning him down after giving him my number, he's a nice guy who doesn't really have much experience with women, and that maybe I should give him a chance. I do find him attractive though he's not my usual "type," but surely this isnt the way a decent person acts? I have a feeling he's just nice to me when texting/"punishing" me by spreading rumours to mutual friends and ignoring me in order to try to manipulate me into sleeping with him. How can I stop him acting like this and deal with it whenever I see him (b/c we're coursemates I can't just avoid him?) If I'm mean to him, a lot of our mutual friends are going to think I'm even more of a "bitch," but I don't think making out with a guy drunk means you have to go out with him. He's also very arrogant though you don't notice it at first, I don't want to make a big deal over nothing but I feel uncomfortable around him.

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