I’m inclined to agree with @cookieman; this sounds like low blood sugar. Your brain runs on glucose. While most people in Western society have an abundance (to the point of a nearly toxic over-abundance) of sugar in their diet, the symptoms you describe point in a different direction.
As @Espiritus_Corvus suggests, it’s unlikely that you had a full medical workup (including the blood analysis that would have confirmed or disproved “low blood sugar” as a problem) in the short time since you first asked this question. I don’t doubt that you saw a doctor, but I expect that the doctor’s examination was no more than superficial: height, weight, blood pressure, a superficial check to be somewhat certain that you’re not suffering from a drug overdose or bad reaction of some kind, maybe check your eyes for evidence of trauma or concussion, listen to your tale of woe about school work not done, and then send you on your way with a “diagnosis” that you’re suffering from anxiety and stress from the pending assignment.
In other words, he probably expects that you’re the same neurotic slacker that he sees day in and day out with similar stories. Except that your description of symptoms sounds more serious, and not simply the result of putting off a school assignment.
Read the “symptoms of moderate low blood sugar” at this link and see how likely that is. Try to see the doctor again (or another one, perhaps) and tell more about the physical symptoms you’re feeling – if you can stay focused well enough to do that! – and ask that blood work be done. You might set a tablet browser to this link and let the doctor read your initial question and your own responses in the thread.
In the meantime, have something to eat, and some fruit juice, perhaps.