First of all, whatever you do, do NOT *****. Things will get better (everybody told me that and I never believed them).
My advice is easier said than done, but it might help.
You need to understand that your thoughts are not reality based. If someone talks to you or says hi to you more than once, then you should make an effort to talk to them, and if that means thinking about exactly what you are going to say, writing it down and praticing it alone at home infront of a mirror, then do it. If you feel rejected, ignore it (I know you can't but don't stop interacting with the person). Don't stop talking to them until they clearly and verbally reject you to your face. This applies especially to girls who might be interested in you. Keep trying to make a conversation with them, and plan what you say if you have to.
Its easier to meet people if you put yourself into situations where you can meet people. From there people still might not talk to you, but eventully someone will ask you why you are so quiet, and then you can just tell them its difficult for you to talk to people.
Lastly, its not that easy to get a girlfriend. A girlfriend could make this better or worse or not affect them, depending on the girl.
