Why don't you just find a girl that you're friends with, who doesn't have a boyfriend, and ask her to go? I am sure there's girls out there in your school without a date that you get along with. Most girls aren't going to ask you, you have to ask them. No one is going to know that you're interested unless you ask.
And, if you can't find a girl, and you don't want to be a third wheel, you don't have to go to homecoming. (I never went to any of my school's homecoming dances. . . maybe it was because we had an awful football team. . .

I don't feel bad about not going now, and I didn't feel bad about not going then). For my junior prom, I went with a girl I was friend's with (we didn't go as a date, but because we were friends), and senior prom I went with a guy who I wasn't dating--it's more fun going with people who you're friends with instead of as a date.