I'm sorry you are feeling so crappy! I've been in the very same position as you though...more times than I can remember.
I've been rejected more times than I care to remember by guys, I've always had friends that were prettier than me, and I've always struggled with my weight. As a type 1 diabetic, it is near impossible to drop. Its not always easy growing up, but it seems to get easier. I have bad days sometimes, where things just seem like they will never get better. Struggling with a disease like diabetes gets to me sometimes too, so when I get days like that I usually just hide away from everyone.
I'm 20 and I've never had a boyfriend, so don't feel bad! I probably will not have one for another few years either. Sometimes it makes me sad, but most of the time I don't care. Not having a boyfriend allows me to do whatever I want and I won't have any strings attached when I decide to move away from this area.
Sound slike you may need to cut some ties from your friends though. They don't sound like real friends! I've been in that position too, and it feels so good to just cut the ties. Amazingly, every time I've cut the tie with someone, someone new shows up and takes their place! There are so many people to meet out there. Of course, high school can be very difficult! Look forward to graduation, make the best of the time you have left there, and then ENJOY college! I love college. The people are so much more mature and there are just endless possibilities!
Good luck. Remember, there is always light at the end of EVERY tunnel!