In addition to the above poster, I can tell you from graduating university years ago, that that level of schooling can wear you down really quick, with all the studying and info and rushing around. Most people in advanced school look like prisoners of war, dark circles under the eyes, nonresponsive, with even A students like me failing an entire course - in my major - because I didn't know what in the world the teacher was saying.
You are 19 years old, lots of energy. It is only natural that you will give this thing everything you got. So, when you have a problem with classes, it can be VERY frustrating. Frustration can lead to a kind of depression. Therefore, you gotta do what us old people do, and that's SLOW DOWN, take a nap once in a while, do a physical activity several times a week where you break a sweat, eat a big meal every single day, drink extra water, and at a certain time in the evenings, that's when you wind down and follow your urge to sleep and go to bed.
Also, instead of dragging all your homework to your room, stop after the last class and go to the library and study there, as much as you can get done, and then go eat, exercise, enjoy some friends or TV, take a hot shower, dim the lights and do something relaxing like reading, and go to sleep.
I know, this sounds too simple, and how can just an ordinary worn-out person have all these symptoms? Well, I can tell you from experience, step back from your world and look down on it... I say to you, just exactly what do you think you're doing, pushing yourself around like that? Of course you want to graduate cumma sum laude, but the problem is, you ain't in lower grades in a community no more; you're playing in the big leagues now, and unless you learn easily and quickly and have lots of down time, you're chasing a rainbow.
Be realistic in what you can do, becuz when you take your good grades into the public workplace, but then you can't keep up THERE either, well, then your grades don't relfect your true person, and you will take on jobs that will literally run you into the ground and kill you. This is known as having a heart attack. Give yourself a break, accept who you are and work with that, and TRY to have a little fun along the way. I know, it's counterintuitive, sometimes that's what truth sounds like, too easy to be true. Yes, you SHOULD give your best, but don't give it ALL. Save a little for you.
Maybe you should see a Doc in your country. I know it will take time to get in for a visit, so make appointment now, well in the morning! Write down all your symptoms now and add to them if you forget. Better copy your message above email it to yourself and print it out. All the information is listed there and your concerns. You might want to visit your opthamogolist (Eye Doc and not the guy for glasses) also for the vision problems.