How do you gain self confidence from within?

I need strength mentally and emotionally this is my story, if you have deep self esteem issues from constant outside rejection by everyone, and most of the people take advantage of that, and you dont want to be a doormat, how do you gain your self confidence if you also have deep emotional scars from the past, present and future and, how to get your points across and not be too rude about it? because im a nice person I dont like conflict because when I was younger , I had a lot of bad things happen to me, I’m also shy and my dream is that I want to be a professional gospel singer but nobody and sometimes even christians dont want to notice me because im just that ugly. I might be ugly but im cute in a beautiful soul kind of way and I think its funny because God Accepts me just the way I am and loves me as much as everyone else, it hurts to think I will always be stuck in the same spot on the earth never going anywhere or sharing the gospel of Jesus Christ because of this rejection that im getting because I just dont quite measure up. its a very painful thing to be unaccepted and know that youll never be accepted for who you really are. but sometimes beautiful attractive people are nice to be and I will feel like im in the twilight zone because it surprizes me but I wish I could feel beautiful everyday, you know what im saying. So how would you or how do you, if you were me, would you really change your self for everyone else or would you just say if they dont like me oh well. im me and God loves me for who I am and he owns everything.