I am straight, there's an amazing gorgeous girl who may or may not have had a crush on me in eighth grade, whom I haven't talked to since, well, eighth grade. I'm not the most chatty of people; I especially can't make much small talk with girls, and even in eighth grade I rarely talked to her, due to crushing on her myself. I have nothing to lose by talking to her, yet at the thought of attempting such a task my instincts go "lul nope" and I fail to take any action. I've not had a girlfriend before, ever, and though part of me obviously would like such a thing, the other cynical depressed half of me cannot fathom me ever doinganything about it, and as a result I beat myself up over my inability to talk to miss awesome dream girl and make myself feel worse.
Mr. Space Cat, you sound a little bit like 17 year old me.
Before that age, I was a mess of depression and self-doubt. I spurned girls on at least two occasions, not because I didn't like them, but because I doubted myself so much that I couldn't conceive of someone else being interested in me, and was sure it was just something they'd been put up to. I similarly spent years unable to work up the guts to ask a close friend of mine out, despite sharing classes and clubs and hanging out with her for almost 8 years. And as I learned later, doing this had understandably hurt their feelings, and damaged their self-worth too. My lack of self-respect had been making a negative impact not only on my life, but on others as well. I resolved to start forgiving myself for my mistakes and shortcomings, cultivating a person I felt good about being, and generally caring for myself.
I'm not going to pretend it was an overnight change... there was a lot of internal damage in need of repair, and even to this day I'm patching up holes here and there. Still, on toward the end of high school, I had made some progress, and felt like a whole-enough person that I was ready for a relationship. I asked another crush of mine out, a super-adorable and super-smart Amish girl. As luck would have it... turns out I'd waited too long. Though I was in a much better position as a person, many of the doors that had been open were now closed. I was late getting out of the gate, and had catching up to do.
Since then, I've had short-term flings, been rejected, been taken advantage of, had a messy break-up, and two relationships that lasted for a year or so. And though none of them worked out in the long-run, each experience has been one I'm glad I had.
TL;DR: You can't go back and change the past. You can only decide on where you want to be in the future, and start moving toward it. Forgive and love yourself, and always strive to be better, and then you will be truly capable of loving others.
Oh, and never be afraid to try. You level up much faster by doing something than you do by fearing the consequences so much that you never attempt it.
P.S. And happy birthday. And I don't mean that in some polite, socially-mandated way. I wish you the best in life in the years ahead... we're all in this together.