I want to get into med school but I remember next to nothing when it comes to chemistry, biology and math. My skills in memorising stuff are shitty and I have problem with staying concentrated. Help?
----------> Khan Academy <----------
Perfect for what you're seeking. It's free and adjusts itself to your learning/learning pace. I can vouch for their math courses (amazing, I wasn't good at math before), they also have Chemistry and Biology courses.
Inability to remember and concentrate are classic symptoms of depression.
Depression aside, do you know any ways I can sit down and study and actually understand what I'm studying?
Or maybe I should just give up because it's quite possible I'm too stupid, eh
Personally I find it helpful to take myself away from home and go to the university library to study. There are too many distractions at home, and I always end up visiting sites that I'd never dare to in public (i.e. porn, 4chan).
Set yourself realistic goals. Give yourself a daily goal, and break that down into lots of different sub-goals. Try to work in 1-hour chunks, and aim to get through one of your sub-goals each hour. Once it's done, reward yourself with a 5-10 minute break - get away from the computer, have a snack, stretch your legs, etc. Also, try to become interested in your topic. It may sound boring, but to the person who wrote it, it's probably a passion. Can you become equally passionate about it?
If concentration continues to be an issue, try drinking coffee and/or eating green apples. If that doesn't work, you might want to consider using a drug like Modafinil for some chemically-induced concentration. It's probably frowned upon, but it's relatively harmless and commonly used by professionals who need to stay alert for long periods of time. I'd suggest you don't overuse it though - it's better to learn to be able to concentrate without having to resort to it.