Guy blushes when I look at him? Is he shy or interested?

So there's this guy in my class and we had to do a group activity and every time I looked him in the eyes, his whole face turned red. He's also sat next to me several times in a row (it's a huge 100+ class) and I catch him glancing at me every so often. I know he has a GF but it seems like he might have a thing for me... or is he just shy?
Guy blushes when I look at him? Is he shy or interested?
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