Is he gay and how should I ask him out?

I like a guy . We're going to different high schools , but I really like him . I've been texting him a lot , and he knows I like him but he's really sweet and he doesn't mind me liking him . He flirts once in a while , and I would think he likes me . But , he doesn't act gay AT ALL I mean I'm against stereotypes and all but ... He LOVES sports , he doesn't care about what he wears , he doesn't walk or talk gay , nothing . Do you guys think he's gay and likes me or he's completely straight and just teasing me ? And also how should I ask him if he's interested me . I would have to text him since we don't see each other since it's summer .