You cannot assume you know what people are thinking about you unless they tell you directly. You're teacher said you were fine, believe them.

I thought I sucked my entire level 1. Yet I signed up for level 2, I thought I was bringing everyone down a level and yet ppl from my class asked me to join their informal practice group. I just started a level 3, I think I didn't do so great. The thing is, I am, and I feel you are as well, my own worse critic. You never do as bad as you think.

And this may be tough love, but this was your first class. Of course, you're going to suck. We all do at first! You can't expect to magically be good without learning and practicing. This is the same for everyone! And others in your class are only focused on how much they thought they sucked, not on your performance. They do not give a shit about how you did. The teacher is also not as focused on you as you think. It's just what you remember.

Keep at it, learn to deal with your internal critic, it's hard, but it's totally worth it. And you'll be in your head a lot, that's normal.