I'm crushing on a taken guy.

So me and this guy became friends this past year and I started to like him because the way he acts just has a flirty nature. He is so nice to me and a lot of the time I feel like he's flirting with me but can't really tell. I would for sure go after him but he's been dating this girl for about 8 months now. But we talked about if they've done anything together but all they've done is make out. I don't know what to do because my feelings aren't going away.