Biology is a topic where you probably have to remember a lot of disparate stuff for the tests. You might enjoy to watch this video, it's a talk about memory techniques given at the Charles Darwin University (on the YouTube IMPSatCDU channel). The talk is called "Jonas von Essen - How to Get An Awesome Memory". (He's a world champion on memory techniques.) He also mentions in passing a book called "Memo: The Easiest Way to Improve Your Memory" by Oddbjorn By. I have the book. It's really useful. Someone wrote about the book on Amazon: "Thanks for a life-changing book. It saved me when I was in trouble. In my second year of university I failed on two exams. I panicked. But then I read about your book, and that made the whole difference! Fantastic!"
Also, do you use Flaschards? There are sites where you can put Flashcards online, and that way you can study on your phone when you're on the move and use short snippets of time for studying or rehearsing.
You might also want to organize your note taking along the lines of Cornell Notes, it's a special techniques for effective note taking. There's one example (amongh thousands) about "Taking Cornell Notes in AP Biology" on the Michael Laudersmith YouTube channel. I don't know why I wasn't taught this technique back in school. Not having good study techniques made me flunk nearly all exams during my first year at university, and depression made me stop studying altogether, until I realized I couldn't have it that way - and regrouped.
One thing to also know about is that repeated test taking is very efficient for learning, even if you have to go and look up the answer from your books in order to reply to those questions. Reading a text over and over again is not. So you might want to work on problem solving as much as possible rather than just read stuff a repeated number of times.
Finally, if there's a concept you don't grasp, you might want to look at e.g. Khan Academy on YouTube. Even if you're working on something complex, like Adenosine triphosphate, it's on that channel. The channel is huge. The MIT and other universities also have a lot of stuff online 'published under the creative commons license' so you might well look into that if your own lecturer isn't any good.
If you watch these two videos today, the ones about memory techniques and note taking, and also check out whether flashcards is something for you (I've been using Cram.com but there are other providers) you might well have improved your study technique tremendously or at least found a path forward. Also, if your current class feels tricky, check out if you can find something useful on the study topic on the Khan Academy channel, and see if it helps. Even if it's something like Adenosine triphosphate, a rather narrow topic it would seem, it's there - on Khan Academy.
Maybe you then won't need those antidepressants. Also, you're just thirty years old, so it's not likely you have a worse memory than anyone else even though for time pressure you might want to be well organized when taking classes. (Says the one who takes classes on the side rather continuously, it's my hobby.)