Getting pissed everytime I see closeted "friend"

I'm 18 now, but last year, I was new to a highschool and was a junior. I became really close friends with a popular guy who was quirky and fun, but could also tell when I was feeling down, which was very rare for people.It started off platonic, he'd talk about his girlfriend and how much he loved her, to how he was breaking up, ect ect. Basically all his girl problems. I thought he was straight; he was what you'd call a lumber sexual, which a beard and muscles to boot. But he'd have moments when he'd act like a sassy girl, and would cover his nails with markers in class, then wash it off.Then it got weird. After he broke up with his girlfriend, he started calling me beautiful. Started complementing me in a way that didn't feel genuine, but flirty? But I told myself he was just teasing, it was NBD. Until he asked me out on a date.I freaked and and walked away, totally at loss of words and blushing. The following day, I texted him, "were you serious about what you said?". I didn't ask specifically. He said he didn't know what I was talking about.I kept my lips sealed about what had happened. A joke happened between him and a few friends, who jokingly asked if he was bi. He freaked out and started screaming about how he wasn't.I ran into him in the hallway yesterday, and just got so mad. Everytime I see him, my day goes down hill and I get agitated. I guess the question is, what now?