Wrong Signal or What?

There is this guy. I've been crushing on him for four years. For me, I know this is love. It's not just any high school infatuation because it can't be. He already has a girlfriend but I can't help imagining a future with him. He only talks to me whenever we're outside the school or completely alone. And when we talk, I can really feel the connection there. He sometimes flirt, he interferes with my personal life when he has the chance, so what does that mean? I'm sure that he's not just doing it as a friend because whenever someone points that out, he's bothered by it. Wouldn't talk to me for a few days, then back to normal. I keep thinking that maybe he's sort of attracted to me or maybe this love is not just a one sided thing. I keep hoping, but the fact that he has a girlfriend just blocks it. So am I just being delusional? Am I taking the signals wrong? Or he does feel something for me?

First: you are not in love
It feels this way I know but you have developed a serious crush/ obsession
People call this oneitis
There are a lot of cures out there

Second: I do not understand what you want? Sympathy? You have 2 options: leave your situation at what it is or go do something about it( like meeting him)
Choose

yes it IS an infatuation and NOT love - why? because it's only 1-sided. Love is not 1-sided.
think of somebody you woudl never be with and have zero interest in getting with. Now.. if they want you bad enough is it love? is there a future? exactly.. NO.

that's what's going on here and you are the person wanting bad somebody that has zero interest in you that wil never change.