Sorry, somewhat ignored the comments posted besides the OPs as I'm short on time.

I'd try to find out the things that you DO like about yourself... and own them. Absolutely rock them, whatever they are. Physically or not. Focus on those and building up your confidence around them.

Confidence is really that thing that stands out, and it's so hard to find out when you've had people tearing it down your whole life. Which is why I'd suggest focusing on the things you do like - going "hey, all of my rocks!" just feels like a big old lie and it's way too much to do at once.

Once you have confidence, you'll be more attractive. I'm not sure how that works, but it does. As does being hygenic and being as healthy as you can be. Not being healthy to look better perse, but to feel better - it builds confidence knowing that you're living your life the best that you can be. The confidence shows in the way that you carry yourself I suppose!