It's a physiological reaction; it's not something you're going to be able to consciously control. You're just going to have to get used to being around boys and the things they do and say. (Sounds like you don't have any brothers...)
Hahah I'm the same way, & I've heard that its cute. I just try to stay chill and like its no big deal.
You can't. They probably think it's cute, lol.