Please help me, I don't know what to do?

There's this guy that I like for 4 years. I haven't talked to him every since last year because we got separated. Last year I told him that I liked him and he just told me he had a girlfriend I haven't talked to him. Lots of my friends pressure me about asking him out because he's single again but I don't believe that. This year I have him for one of my classes and lunch. I've been noticing that he has been acting weird lately. I catch him looking at me during class and lunch. Sometimes I even meet his eyes but then I look away because I'm scared to look at him. Another example that he has been acting weird is that today during lunch, since we have the same class before lunch we come out at the same time, he got out of class first and while I went to the line he waited for one of his friends that was right in front of me. I panicked so I tried not looking at him. I want to talk to him but I'm too scared to do so, please help me!!!!