Been in love for 3 years and still didn't confessed.

I think i fell in love with a guy... Idk if I am but I believe so... I knew him, for at least 3 years. We had a type of hate relationship (we would always pick on each other, make fun of each other in joke, it was never meant to be mean) At first, I thought he was annoying, he would always joke and be loud. But slowly I find him adorable and he didn't annoyed me as much as before. Before I knew, I couldn't stop thinking about him. I never once thought I was beautiful. I'm a tall girl, taller than him and I always thought I was ugly. A year later, he was still in my class but we had a good distance between each other. (We weren't friends, just like classmates) I continued to watch him in class. But then I found him kissing a girl in the corridor. I was with my friend so I couldn't show that I was hurt. Since I always told them I hated him and he was annoying and kept the appearance of hate (even tho i liked him). Sometimes I cried thinking about him so yeah, i guess it's love. So its now, I still watch him and hope he would talk to me or even look at me. He already has a girlfriend and i don't think he was or is attracted to me. I plan to confess him when we graduate from school, if he doesn't have a girlfriend, but I'm scared.