I understand your difficulty. You described me about 3 or 4 years ago. My confidence would fluctuate wildly based upon my mood on how others responded to me. I could feel myself glowing when someone laughed at my joke, especially if a lot of people did.
I could feel myself getting gloomy when I wasn't the life of the party.
Now I tell myself to calm down when I feel praise from other people. I tell myself that their praise doesn't define who I am. It lets me feel calm. It also keeps me from getting too big of a head.
I think one thing you ought to do is to do things that you are afraid of doing. That seems to help my self-confidence out. I hit on random women a lot. It's really tough and scary most of the time, but it really helped me build the confidence that I need to hold a conversation with an attractive woman. I should probably take my own advice and do other things that scare me, but eh...maybe one day.
Also you should hit on a ton of guys! I find it extremely attractive when a girl hits on me. (It's never really happened, but I have had a girl pursue me). Ask someone to go walk with you. Tell a guy that he looks handsome. Tell a man that you like his shirt, etc. It's not creepy for a girl to hit on a guy. All guys will be flattered. Some guys might be a bit rude about turning you down, but that's ok.
Also get a meetup.com account.
And check out http://www.improveyoursocialskills.com/ I think Nick is friends with the owner of that site.