I always feel embarassed and can't stop cringing at myself?

Sounds to me like you are a class clown. It is good that you stand up for yourself. Look at me. I'm the shyest guy at my school and don't let anyone mess with me kind of like what you did. You definitely have social anxiety, like me... I'm 16 and have very few friends. Sometimes I regret speaking up for myself, too. However speaking up for yourself will show that you stand up for yourself and that you aren't a doormat! As for people liking you, show you are approachable and that you are nice person to get along with. Hope that helped.