Always feeling small

I love myself i really do,but when I am around others I always compare myself and all my flaws. I I always second guess what I should say or should not say, so that I don't offend anyone and i always try to make myself look small and blend in with the crowd. As a result i always feel left out and as if i am not good enough as though, there is something wrong with me. I have never been confident, and i want to make a change. Where do I start?