Been there. Math is fucking hard. And on top of it, the pressure to excel and compete can be intense.
I've been working on degrees in math for 7+ years now and I have failed a lot. And I mean tanked a midterm exam. Got a 40% and begged my professor to let me do extra work to make up for it. I withdrew from my advanced math program because the pressure was too high and I was killing myself to keep up. I'm not the brightest. I didn't get amazing internships like my classmates, and I got rejected from PhD programs my first try.
But here is the amazing thing. Through the struggle, all the math you are learning accumulates. It piles up in your brain, regardless of failures.
Math is like this at every level. Always pushing you in some new way. Making you uncomfortable and confused. And you will stay confused until you put in the work to solve problems on your own. And because you are so wrapped up in the difficulty of learning, and comparing yourself to your peers, you don't ever see the huge pile of math skills you have stored up.
Right now, you are learning calculus. That is amazing! Think back to how much you knew about integrals/derivatives a year ago. I bet that you know so much now. See! You are accumulating math skills!
It's not easy. Institutional benchmarks and gatekeeping get in the way of the learning process and cause a lot of fear and uncertainty. But you can navigate them if you are patient.
Be present with the feelings of fear and anxiety and acknowledge to yourself that this feels important to you. Then take a breath and give yourself some room to be imperfect. You will get there eventually.