Why is he always watching me?

Okay, this guy and I have quite a history.We went from friends, to best friends, to having crushes on each other, back to friends, then to friends with a few benefits. We'd fool around quite a bit, but we never had sex.

Soon after rumors started going around, and they turned him against me. For five months he hated me, and I wasn't about to plead with him to forgive me. Everyday, every time he passed by my in the halls, he stares. If he sees me, he'll watch me. Its not a glare, but I really don't understand.

We started talking a few days ago, first time in five months, and we got onto the topic of what happened. He said he might be able to forgive me, but it would be hard.

Then, while we were talking about a mutual friend of ours, he wanted to know why I wouldn't date this mutual friend. After talking a bit about why I didn't want to, he said, " if you pass it up I might not wait any longer"

After a few seconds of silence from me, he corrected himself. I think it was an honest mistake, but my best friend doesn't think so.

So, why does he always watch me?