Do a little "spring" cleaning, find all the clothing you like but never wear and put that in a box. Surround yourself with things that make you comfortable in your own body. If you are conscious about your body this will help a lot. If you only end up with three shorts/pants and two t-shirts who cares. Wear the same clothes a few times as long as they are clean. Almost no one will notice.
Diet can do a lot. I know its not like you are trying to lose weight or something but eating healthier can make you feel happier and more confident. Waking up with a clean hydrated body can make you feel so much more energized. Eating can go along way.
Like i said you might not be trying to lose weight, but going for a walk/run or doing some yoga in the morning might just do the trick. Who cares if you have lost weight but someone should care about how much more strong and happy you are. If exercise is a drag for you find small ways to work out. When you might be watching/reading something, do a little stretching. Your body will feel more loose and free making your soul fee loose and free. (Not to loose though)
Try to surround yourself with people you love or feel happy around. Make all the small people count. Try to distance yourself from the people who have brought the feeling of self consciousness to your mind. Try making new friends or going somewhere you know and love. The people around you are a big step to confidence. Take a brake from the sour people you see every day and find some sweet people.
If you are worried about your smarts this is a good step. Say you feel that your writing game is failing you; do a writing exercise every day, find a prompt and challenge your self every week. Struggling with math confidence; Try out khan academy; A online program (free) focusing on teaching math skills and trying to challenge its users (Not only math)
History?; Get some cool books about cultures and history at any book store. Don't leave em in the corner flip them open and start reading.
You can think negative if you want. Do it as long as you need to as long as you can realize you are thinking negatively. Try to think about positive thoughts for a bit also. Your allowed to look in the mirror to, but if you want to think of yourself as beautiful and badass; literally write on your mirror; You are beautiful, Badass, So cool, Smarty Pants, So hot. Now when you look at yourself you can think awesome thoughts instead of negative ones.
There you have it. My tips for self confidence. If this didn't help; sorry. If it did; Good for you/me. Have a great Monday night- Lulu