What does it mean when a guy is always around but rarely speaks to you?

There's this guy I'm into and I've known him for ten years and we use to be friends in grammar school until we grew distant. We started having classes together the last 3 years and we occasionally talked and joked with each other but nothing really happened. This year we have no classes together per se, but we're always in the same room, or area of our school.

Anyway, since school started, he's been walking really close behind me and my friend when we go to class. I mean, one day I glanced over my shoulder and got a big eye full of his chest. In addition, he'll ask me about classes I might be thinking about taking. For example, he asked if I was taking another version of a course we used to take that got canceled. At first, I didn't think anything of it other than he was curious, but then we had a combined music class where he met my music teacher. After class he ran up to me and started to joke with me about how scattered brained she was and how much he reminded her of our childhood bus driver due to her awkward expressions. He seems to only talk to me when he has an "in" or an inconspicuous reason. Other than that I only seem him lingering around nearby. In the cafeteria when I'm looking over and checking him out, sometimes I see him look over my way out the corner of my eye. And in the computer lab, he sat next to me, a mutual friend in between us. After about 20 minutes, he finally asked me if I would go to our club activity nights again, which spurred a long and fun conversation for all of us, but mainly between me and him. I was exited, but I already knew he was asking other club members, so I didn't feel like it meant anything, but I still was wondering why it took him so long to ask me since he got all my contact info just yesterday and still needed to speak with me in person. It was just that after our friend left and I was still sitting there, there was this weird tension and he kept coughing or making noise or some sort. I eventually left because I couldn't work with him there because it was distracting and weird to think about him while he was right there.

So, I've been racking my brain over this long weekend trying to figure out what it means when a guy is always around you but rarely speaks to you. He's always nearby, or around, but we don't really talk that much. When we do it's really fun and we just laugh. Last year, he used to jump into conversations I was having with a bunch of friends, but I just can never imagine him actually doing any of this because he likes me. I had a theory he just wanted to become friends again, but I feel like if that was the case, it should have happened by now.

Can anyone give me any advice? Because I have no idea what to think anymore.

I'd really like some input from guys. Anyone out there willing to help?