Guy's Behavior

The "popular guy" gives me lots of unwanted "attention". Why?

I'm a new student and I noticed that this one guy tends to give me a lot unwanted attention: a couple of times already, during attendance, he turned around to look at me when it was my turn to say "here" (he sits two rows in front of me), during class he randomly turns around quickly to face my way for a split second then starts doing something else, when someone behind me or near me says something he looks at the person speaking but glances at me every few seconds, when a teacher asks me a question he fully turns around to stare and even moves with his chair to get a better view of me. I talked w/ a girl that knows him a bit more and she said that "it took him months to say hi to her in public", but he always waves at me or gives me the "bro nod" whenever we see eachother in public, we've only been classmates for 5 months and he knows this girl for 2 years now. I had to text him once about school once and he was cold af and replied with only 2 words (no hi/hello, no thank you, no please, nothing). His friends straight up ignore me, it's like I don't exist in their eyes (which I don't even mind). He's a very good-looking, popular guy and has had lots of ex's, numerous one night stands and love messages from admirers while I am very bland and (let's be real here) unattractive, pretty much the opposite of him. Everyone I talked to about my situation told me he "likes me" or something similar, but I highly doubt it. I even asked him anonymously (on a site similar to ask, he has in his insta bio (I'm not a creep D:)) whether he has/has had interest on classmates and he just replied "nope". I'm perplexed. I don't look out of the ordinary so I really don't understand what could make him do all this. I'm very self conscious and he gives me a lot of anxiety. Why is he acting this way? Am I just overreacting over nothing?
The "popular guy" gives me lots of unwanted "attention". Why?
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