Why does he ALWAYS follow me with his eyes so obviously?

Anonymous
Last year I noticed this guy I found attractive and I looked at him. Then he started to look at me a lot, stared at me, even when I wasn't looking. We made really a lot of eye contact, always deep and intense ones.

This year, we still look at each other this way. Then, he showed me to his friends, I overheard them saying I was hot (I've never caught him checking me out). A friend of him pushed him towards me, his friends watched me everyday. The guy stared at me even more, even when I wasn't looking, he stalked me, trying to be where I was and walked past me as many times as he could. Everytime he was walking past me with his friends and didn't look at me, he looked down smiling. Same if I walked past him.

But then, I discovered he has a girlfriend. I wasn't angry or sad and I naturally started to ignore him.

It's been quite a long time I do, but he still looks at me as before. He watches and stares at me for a really long time when he thinks I'm not looking. But once I catch him, he looks away really quickly, looks down kinda nervously.

Now he follows me with his eyes (and turns his body) from afar (he's at a place he can't see my ass). It's so obvious when he does, but I pretend to not see. He does it in a more discreet way when he's with people.

Why does he still look at me this way?
Why does he stare so long when I'm not looking?
Why does he look away nervously and look down?
Why does he watch me/follow me with his eyes from afar in such an obvious way?

He is two years older and we have never talked.
Why does he ALWAYS follow me with his eyes so obviously?
2 Opinion