I don't have specific advice on what to do but I've experienced this before.

It can be overwhelming to look at teachers directly, especially while they're teaching! You don't have to do that. You can look at them only occasionally, and even then, just avert your gaze slightly. You don't have to stare down teachers directly (I know I am exaggerating and I don't mean to make light of your issue when I say to stare them down). I just mean that you don't have to look at them directly a lot. It's good to show that you're engaging in class, but feeling good about yourself is step one. Also, think about this: teachers are there to teach (they're the ones that are employed to teach). They are probably feeling an equal amount of pressure as you may be putting on yourself. Having been a teacher myself, I know this is true in most cases. In my case I always felt a certain degree of nervousness when teaching (not to the point where it was debilitating, but a bit of nervousness).

Anyway, I hope you find some support with your issue! And relief!