What does it mean when a boy is always staring at you?

There is a boy at my college who I liked a while back, around the beginning of the school year. It didn’t last long, and I am quite discreet when I like somebody so there was little chance he knew. A few months passed, and I have noticed this boy staring at me more and more, to the point where I look back at him and he carries on staring. This has been happening for a while now, and I tried to write it off but as time goes on I feel like I see him everywhere around college -although it’s pretty small- and he is always staring at me. It’s quite intense too, he stares with like 0 emotion, and doesn’t even smile, so it gets to be quite awkward. At first I thought it may be a coincidence but as time goes on I am more and more convinced that it isn’t. I am not objectively pretty or anything (I’m my opinion anyway) and I haven’t spoken to this boy since I was in a random lesson with him in secondary school, so I don’t imagine he would have any reason to like me. What does it mean when a boy stares at you?