There was no such thing as homosexuality until the 19th century. Gay/bi/straight is a modern social construct and, perhaps, not accurate. In prior times people just saw other people as sexual, capable of sex with either sex. Some of the lovliest poetry out of the Islamic empire comes from men writing about beautiful boys. Were these men married? Yes! Alexander the Great was married and had a beloved male friend with whom he had sex. There was no dichotomy. The history of sexual identity is rife with men and women and whole societies who understood that most people could go either way at any time.
Worry less about labels and focus on what you want.
Lot of times when rejection is consistent, guys are asking out the wrong girls or they're going about it the wrong way. They're attracted to women who, otherwise, most men would reject because they're unavailable for one reason or another. When it comes to having a big dick the men on this board will tell you time and again to take it really slowly. Keep your jeans on or the lights OFF until just before you go in, get her really wet, use lube even if she's wet, don't use just one finger to finger fuck her, make sure she's loose and relaxed (relaxation on the woman's part is very important). Being a good lover with a big cock means you have to do things for most women that other guys don't. Yes you may find a size queen who will have no trouble taking you, but most likely you'll have to work it.
You're not gay because girls don't want you, you're not straight because girls don't want you. You're a guy looking for a girl who won't say no. That's entirely different. If you're hot for guys then that's different as well. Don't confuse the two or else you'll end up on a big cock forum wondering if you're gay because chicks won't fuck you :wink:.