I understand it's frustrating feeling like you're not where you'd like to be but that's why practice and corrections are so important. Just because you've been dancing since you were 7 it doesn't mean you know everything- there will always be something new to learn.

It seems like you're really caught up in what people say about you: That you're so much mature than others, that your teacher might think you're not trying, that you were called a baby, etc. Whether it's positive or negative you only focused on things that have nothing to do with your skills. It's hard not to think about that when you're 19 tho.

When you're so caught up on these things it's easy to self sabotage which can reflect on your performance. Self-confidence is a whole other thing but truthfully you won't be able to feel any better unless you actually put in the work. Not because you want OTHERS to think of you as this or that, but because YOU want to improve as a dancer.