He has a gf ... I'm confused :/ ?

There's a guy in my school who I haven't stopped thinking about. I don't know if I like him but here's the story. We're basically in a lot of cles together this year. We only started getting close when we would talk on MSN. We discovered we had a lot of common interests and so. But thing is, we talk heaps and heaps on MSN but at school, we rarely speak, it's only a smile or a ''hello' we give each other. I guess the reason to this is because I am a very, VERY, quiet & shy person. On MSN, he gets very concerned about me. He sometimes asks if I'm feeling OK and asks about my personality. He has said that I am a very kind, sweet and lovely person. One time, he gave me a gift for no special occasion. Though I knew he had something to either say or give to me, but it took him almost a week to do it. Just a few days ago, he started to play guitar during music cl, and when he played, he kept looking at me. My best friend has said that everytime I walk past, he looks at me. And she has told me that he smiled at her once. But one time, I had to work in pairs with a different guy and that guy started asking me to sing him a song and asking me if I could cook then the guy (one I am concerned about) kept looking at us. Thing is, he has a girlfriend. They broke up and recently they got back together, but now I'm not sure if they're still dating. Though I saw a few days ago, she was hugging him, putting her arms around him but he wasn't putting his arms around her. Then she started puting her arm with his arm but he looked at me and just went with her. I guess I consider him as a brotherly type. But it's a little awkward, with the way he acts. I don't want to seem like I am trying to ruin their relationship. Maybe, I am just overexaggearting. Maybe he just considers me as a sister like figure? I don't know. What do you guys think?