Well, wait a minute. Are you actually supposed to memorize things? I don't think anybody in school should ever try to memorize something unless they are specifically told to do so. Memorizing things for school is a BIG mistake that a lot of students make, and it rarely works, even for people with good memory. You may actually need to change your learning habits more so than anything else IMO.

I'll tell you this from experience: If you 100% understand the material, there is no need to memorize any of it. You will be able to remember it very easily, even with memory impairments. For example, think about when you first learned to write: someone told you how to write and then you practiced it until you understood it. Now, writing is second nature to you. That is, you don't actually spend time going, "oh... how do I write a W again?" or "When do I use a pen or a pencil?" You understand it.

Also, here's a fun learning tip I learned from a highly intelligent peer of mine in undergrad who went on to receive his MD from Harvard Medical School: it often helps to write "recipes" for things that involve processes. For example, when it comes to math, there are always a bunch of steps involved in solving a problem. What you do is write "recipes" (i.e., words) briefly describing what to do. e.g., "Step 1: Add the two numbers together. Step 2: If the sum is greater than 10, then follow to step 2a. If not, follow to step 3." etc. etc.. So the idea is to break things down... to really simplify them.

I'm not trying to be mean, but memorizing has soooo many downsides because memorizing is not learning.

BTW, what also helped me was making study guides and altering my class notes. Basically, I'd write my notes during class and leave extra space on the left and right columns. Then after class, I'd go through my course books (or online) and try to breakdown what everything in my notes meant. Then, I'd have a bunch of pages with lots and lots of notes on them. From there, I would determine the "important bits" and create a study guide out of that. Then if I was confused about something, I would refer to my notes with all the details. But otherwise, I could use all the study guides that I created for each test to review for my final exam to make sure I understood everything.

Sorry for the long reply, but I thought it'd be worthwhile to mention learning habits so that you're not wasting your time memorizing things and getting frustrated with having poor memory. Best of luck.