I hate the fact that other people hate their lives, and I guess that's part of my life...
But seriously pal, chill, shit can get rough and life is hell, there is no can't when it comes to moving on from a love interest, there is won't or don't want to, simple, go out and find someone else, you'll forget her eventually, whether you want to or not.
And as to whether it's possible to be have a crush on a dude and a girl at the same time, well if you're bisexual I can't see why not, straight guys can have a crush on 2 girls simultainiously(happened to me once or twice), so I fail to see a difference there.
But seriously, if you wanna be happy only thing you can do is BE happy, your life is quite simply what you choose to make of it, sure you may not control all the variables, but how you handle the one's you're presented with, and what you choose to do with what you got on hand, is all that matters.
I'm a broke, highschool droppout, workin a dead end job and barely payin my damn bills, but I choose to LIVE and to love, and to have fun whenever possible, I turn my job into an enjoyable activity, by being as positive, flirty and funny as I can be while serving customers, time flies, I enjoy my time at work, and I get relationships buildin every day with my regulars, I've made good friends through work previously.
And how does it affect my dating life? Fan-Freakin-tastically, if you're a positive and energized person, and stay in control of yourself(like know basic social etiquet, and don't like, force yourself on people, hang back and relax), generally you get results, with ease, if you're bummed out all the time, you cannot expect to get dates or have someone want you, why? Because if you can't make yourself happy, you can't make anyone else happy, simple, you become a downer to those around you, and that doesn't help your love life AT ALL.
My advice? Take it easy, life can only get you down if it ends(and that down is bein buried), or you let it. Go out meet a buncha new people, the more practise you get dealing with people you find attractive in a casual(not obsessive and possibly creepy) way, the easier it gets to just have fun, and attract those you want to.
Cheers!