You could find your teacher when he is at his most vulnerable. Then start firing questions until he gives you an A to make you stop. jk.

Seriously though your teacher is your best bet. You most likely aren't the first and only student that doesn't understand the material. And if you're too nervous to ask your teacher, then perhaps you could try researching about it.

Personally, I resent my teachers so I'm always creating my own bad luck with my studies lol but researching and reading books really helped me out/