(Centuries ago, there was no word 'homosexual', and there was no word 'heterosexual'. Amazingly, magically, this did not result in confusion and fear. If you stop and think for more than two damn seconds about what really defines gender, the situation becomes obvious.)
What's really going on is, you're latching onto someone you know of, out of the millions of mysterious people you don't yet know. This is undoubtedly working against you, considering how easy it can be to meet new people.
(What defines gender? Is it our sexual organs? Is it the way we carry ourslves? Is it the clothes we wear? The way we talk? Is it a collection of personality traits, like aggression, empathy, patience, bravery? Are you a woman because of your vagina, or because of your taste in clothing, or because of your temperment? Are you a man because of your penis, or because of your Ford Thunderbird, or because of your blatant disregard for your personal safety? People consolidate the traits they discover, to justify their identity. At the same time, they also unearth and develop the set of traits that they are attracted to in other people.)
Living in the past, and mulling over previous relationships, is sometimes helpful -- but you've got to remember that, while you're doing this, your present existence is cruising away on autopilot. It's easy to keep airing your old dirty laundry, day after day, instead of braving the marketplace for something new. ... But there's no point, because the old stuff doesn't even fit anymore.
(So people can be attracted to one another for an infinite number of reasons ... Yet our culture devides this attraction based on the number and type of sexual organs involved. The reasoning goes, "since most men exhibit these traits, and most women exhibit these other traits, and since there are only two sexes, there must be only two types of sexual attraction at work." Clearly, this is bad reasoning.)
My advice to you is, regain your social footing as quickly as possible. Renew contact with old friends, and arrange to discover new ones. And since this all depends on your mood, pay attention to it, and take steps to maintain it's health. This is essentially why people say that the most important relationship you can have is between you and yourself. ... All your others depend on it.
(But the bad reasoning doesn't stop there! Some people, especially people who have chosen to call themselves "bisexual", claim that sexual attraction exists on a spectrum, drawn out between absolute female on one end, and absolute male on the other. Since all sexual attraction falls neatly along this spectrum, that must mean that "bisexual" people are able to experience the full spectrum, or at least more of it than those stodgy "homo" and "hetero" people. In fact, they truimphantly claim, anyone who isn't bisexual is actually just repressing themselves, and it's society's fault, and everyone is truly born bisexual.)
If you don't know what you're looking for, then gather more information. It doesn't have to be an answer, just information. And I'm not talking statistics and daytime soaps here, either. This kind of information can only be absorbed directly, by placing yourself in the process.
(Sorry, but the spectrum idea is equally bogus. All it takes is that extra two seconds of thought, to realize that sexual attraction cannot possibly be mapped onto a one-dimensional spectrum. The rainbow flags are a great symbol, but they also piggyback this unfortunate concept along. You know what I think accounts for the confusion in the hearts of most people who call themselves "bisexual"? They find themselves attracted to a lot of people, and so, sorting out their preferences is a very difficult, often contradictory, mess. As general grouping terms, "hetero" and "homo" and "bi" are doing a disservice to the flexibiliy of sexual attraction. But they have to die a long, painful death, if they ever go at all.)
Pull yourself out of the past, and consider each day on it's own terms.
Pull yourself away from the idea that the meager handful of people you have already met is all you have to work with in the whole world.
Pull your needs and opinions up from your mind and place them where people can see them, and give them a chance to react the right way.