I was in a similar situation in college. What helped me was to do /every/ problem in the homework and check them -- many math books will provide answers to even or odd numbered questions. It sounds like a drag (and it was), but I also finally passed with a very good grade!

Also after you've done the homework, make sure you consult with your teacher about things that troubled you. Having battled your way through so many examples, you will be able to appreciate their explanation better than if you never tried them.

Good luck!