You should realize that almost everyone feels lost or confused in their class at some point.  

Here are your steps to fix your problem:

1. Ask your teacher for help.  SOON!!!!!!!!!  Waiting to get help allows the problem to get bigger, and makes it that much harder to fix.
2. Take your teacher’s advice.  Your teacher might recommend going to a tutor, staying after school with them, giving you more practice materials, or another solution.
3. Communicate every week with your teacher and counselor how you are doing. Again, problems are much easier to fix immediately and harder if you wait.