I'd like to begin my reply with the words "Boys are stupid". Because, and I realise this is a sweeping generalisation, they are. They don't notice things, they're insanely insensitive and seem to think that a mumbled "sorry" is sufficient (pardon my own intensly heightened hatred of males at present

)
You didn't mention if there's ever been anyone you've really liked enough to want to go out with, and if you have, how you acted with them. Guys need things spelled out for them, they don't "do" subtly.
And please don't ever thing you're not worth something. I used to feel like that, but I guess, (impending cliche) that you have to learn to be confident in yourself and like yourself before others will be able to like you too.
I know it feels bad when your mates have all got guys after them, but wouldn't you rather not try and rush something and have it mean very little or wait until there is someone you really like and have it mean the world?
Everyone gets lonely from time to time. I've been single for months now and the novelty is wearing off - I want someone to talk to more than anything. For me, a friendship is far more important than a romantic relationship. You get on with lads, so just be yourself with them. One day, one of them will realise just how wonderfully special you are, and will hopefully treat you like the princess you deserve to be treated like. Until then, dont fret about it. As they say, it happens when you least expect it.
But please don't let it get you down. Emerse yourself in your friends and have a good time. Life is far too short to be worrying about things like this, I promise!
*hugs*
I hope you feel better.