Here's a simple test you can memorise:
As a man, if you like women, and only want women, you're heterosexual. If you like men and only men, you're homosexual. If you like both, and want both, you're bisexual.
An interesting fact is that in my trade (sexual health) people working in the real world (not academia, and not on the internet) don't talk about "gay/bi/straight", they talk about Men Who Have Sex With Men (or MSM), because so many men who have sex with other men still self identify as straight - personally I feel that this is most likely due to stigmatisation of "gay = rubbish".
The "gay community" (whoever they are) are sometimes cited as being hostile to bisexual men - one gay friend told me that many gay men see sexuality as totally polar, they deny bisexuality as strongly as the "straight community" deny bisexuality.
You sound bisexual to me. If I may be indelicate, is your attraction to sex with a man that you are aroused by being fucked or is it more than that? If you like being fucked, have you had a woman fuck you? Was it different/better/worse?
The point is, you could be a straight man who likes anal penetration and mentally see that as something that can only be done by a penis - but I doubt that.
Whatever you do, as with all sexual activity, keep yourself safe - use condoms, use lube, and have fun.
