Well, bi-sexual maybe, but definitely not gay. I think he's confident of his sexuality, whatever it is.
Now who is assuming Michael is fucking Kelly "just because he's black and she is white" ? Why can't they be fucking simply because they're attracted to each other, and their race just co-incidental? If you've watched Kelly around Michael, however, you do see she has a strong attraction to him ... loves touching him, and playing the innocent, helpless chick, etc. And Kelly, otherwise, is rarely out-spoken; loves being the center of attention, just NOT around Michael.