Could my boyfriend be bisexual? even if he doesn't know it?

I'm worried that my boyfriend is bisexual. I don't say gay because I know for a fact he likes women, but I think there's a chance he could also like men. First of all... hes very feminine. Everyone I talk to, like my friend Randall and Kacey. They seriously thought he was gay until they found out I was dating him. He seems flirty with guys. Kacey is bisexual and he my boyfriend knows it and Kacey liked him, he asked my boyfriend to hold his hand and he did. Later I was like dude what the ****? and he was all "i didn't know he was hitting on me" like he was super oblivious. He also says hun haha... which i actually like but that is a very gay thing. He has a best friend that he's... really close to. my boyfriend is 17 and his friend is 19. They still have sleepovers. They also go on late night walks together and go lay out in the field by our house and talk about their feelings and stuff. One day my boyfriend didn't go to school after sending me a txt at six in the morning saying "well im just barely gettin in bed" later i asked him why. it was because he was with his friend until 6:00 AM. and i was like why didn't you go home? and he said that they didn't want to stop hanging out. a little odd to me. And the when ever my boyrfriend talks about his friend my gaydar goes off bad. he says things like "He really cares about me, when we first were hanging out i was so worried he didn't like me or care about me and secretely hated me" and then one day i jokingly said your in love with him? and he was like yea. he didn't pick up on the joke. i've asked him about it a few times, he always says I. am. not. gay. but he doesn't reassure me very well. he changes the subject really fast. so can someone tell me what they think? and maybe give me some tips on what to do? thanks.