How to not get nervous around him?

So like this guy, but I get SO nervous to talk to him. I don't talk to him because I feel so insecure, I feel like while I'm talking to him there's probably something wrong with my hair, something's in my teeth , etc... just stuff like that. My friend told me that he said I'm really pretty and nice but I still feel like if I talk to him he'll think I'm ugly or something. Please help . I really want to talk to this guy , I really need some advice ): Please help meee!
How to not get nervous around him?
Post Opinion