Wanting to be alone, isolated and hidden from everything

In the middle of the pandemic, I started a master's degree and my problems began: the first, the constant feeling of insufficiency. I was mediocre as an undergraduate, and the professors knew that, so I've always felt this pressure to improve, and I improved, but not much. Now I'm in my doctorate, I earn money to study, and I'm doing a second degree. I can take both.

This leads to my second problem/: I was never able to make friends again. I stay at college all day and I don't talk to anyone, I don't feel like talking to anyone. I want to lock myself in the bathroom. In group work I miss class, I avoid talking to teachers. Regarding the doctorate, the constant interaction with professors is a pain, I keep having bouts of anxiety and fear.

Have you ever felt this way? Do you just want to be alone, in the dark, sometimes hidden, in a very small space so that no one finds you? I feel this every day