I'm in shape and other than some marks on my knee's from falling a lot as a kid nothing is wrong with my legs, but I always get really self conscious wearing shorts especially at school. So I usually where skinny jeans throughout the summer in 80-100 degree whether unless I'm relaxing at home...How do I not get self conscious? -.-
Try and piece together a really nice outfit, eg a nice T shirt or top, nice sandals or pumps and see how it works with the shorts. I think the confidence will change when you feel and look good with what you are wearing. I hated shorts at first because I thought it didn't look nice on me although I have the right figure for it and legs. But I was very self conscious about it, I worked on accessories, tops, shoes and hair styles that would compliment my overall appearance and it did help - I became more confident and less self conscious.
I agree with the others. You're young...wear them now while you have more leeway to do that. For me, I used to wear pants or longer shorts at the gym, but I gradually began to wear shorter shorts. And I got used to it. So now it's normal to me. Of course, you want to be decent, but there's nothing wrong with wearing shorts...
Well maybe the heat and the idea of skinny jeans in summer will be the pushing factor to you dawning some shorts which you'd probably keep up because of frustration and just grow a bit thick skinned to your self conciousness! It worked for me. When I look back I kinda just think *?!* It's probably better to go for logical reasoning over making yourself feel better, I think that'll just come naturally after you do it for awhile, you start to care less about it. People really don't want to be going around critiquing peoples looks, especially singling out their legs! ;)
Or you can try looking at it in a fashion sense, try to find something you love about shorts and incorporate it into your ouft*ts! :) Make a goal out of it?