The first step towards real speaking confidence, in my opinion, is self-acceptance. Now, as a British person, I’m used to putting myself down. So I get something wrong and I say, “Oh, you idiot.” That’s not helpful. What I’ve started to do though now is to accept myself completely.
My advice to you is to look at every aspect of who you are, every quality, every property, every stupid thing that you do that up until this point you’ve disliked, lay it all out in the open for yourself, examine them closely, and learn to love all these things about yourself. Accept them. They are who you are. They are part of your identity. If there’s something you’re unhappy about, that’s a weakness that other people might capitalize upon; an insult only has as much impact as you permit it to have. So if you’re happy with everything about yourself insults won’t touch you and insecurities and other things that you perceive people are thinking about you won’t affect you.
So learn to accept, and it’s hard, right? A really difficult thing to do, but learn to accept everything about yourself and you will be invincible, and you will have taken that first crucial step towards true speaking confidence.