Sometimes you need to practice your self-assured body language in order to feel more confident.

When you practice something, as much as you try, you will achieve it somehow. You have to practice your posture, keep practicing and practicing until you make it genuinely without having to fake it. Try staying with your torso right, with your shoulders and head up, like there's nothing to be afraid of. Try maintaining eye contact with people when you are talking, that shows confidence and also, shows that you know what you're talking about and that you're not saying random things.

Standing right and being in a posture that you feel like you are stronger, or without having to be shy about anything, is a practice that I've seen a lot of people using. If you look at confident people and notice their postures, you will know that they are confident just by looking at them.

People can fake being confident but if they practice their postures, they will mentally feel like they have confidence until they get it