Can you make a mental picture of what you have read?
For math,
1. Have your pencil in your hand and do problems while you are reading the textbook.
Read a section of the chapter. Then close the book and hide your notes.
Recite what you remember out loud.
Review the section.
Practice more problems - try them without your notes and book
2. Think of examples from your life that pertain to the formulas. Do this as you read the textbook. Apply the formulas to real life problems.
3. Visualize the ideas that connect.
4. Test yourself. Then look at the errors and figure out what you did incorrectly.
5. Process and summarize your notes rather than leaving them as they are. Do not try to memorize the process. Learn the concept so that you could derive the formulas if you need them.
6. Don't cram
7. Create your own math dictionary so you really understand the terms.
Try Khan Academy for the things you have difficulty with.
Try Sheila Tobias's Overcoming Math Anxiety book.
Overcoming Math Anxiety: Sheila Tobias: 9780393313079: Amazon.com: Books
There is a good workbook, but it is expensive to buy new. It has a CD rom with it.
Abe books has it very cheap:
Conquering Math Anxiety (with CD-ROM) by Arem, Cynthia A.: Brooks Cole 9780534386344 PAPERBACK - Little Caroline's Books