Could my best friend be gay/bi?

Honestly, he doesn't seem gay to me. Obviously he has some kind of insecurity or some sort of unresolved issue because he gets pleasure from bragging about his penis size and gets territorial. He has some kind of issue, but it just doesn't come off as gay to me, and I am gay. The fact that he totally cock blocked you was probably more of a jealously factor mixed with some kind of macho territorial thing, but honestly i just don't feel like he's gay based on what you wrote. It is kind of weird that he offered to show you his cock, so he could be bi, but I think it is more of a sense of insecurity caused some inner issue. I feel like if he were gay, it would be a lot harder for him to sleep around with girls and ditch you if he even sees a chance for sex. I wouldn't be able to be that promiscuous with girls if I were closeted. If his sexuality is the issue here, then it would have to be bi curious or something.