Headache :(

I am experiencing terrible headache AGAIN!!! This is really a very horrible feeling when you feel as if your head is going to burst at anytime… The situation is better when I have things to do in day time. But once I am about to sleep at night, the unbearable pain make me feel so terrible and unable to sleep…
This morning when I was having lecture class for Theory of Differential Equations, I suddenly had a feeling that I am a very stupid idiot. I cannot understand at all what was explaining by Dr Bier although he said that we should have learned all those things in Calculus II. But I really cannot remember anyone of them… Things became worse when he was explaining the theorem proving. My headache attacked me again when seeing those theorems which are beyond my knowledge.
Things still remain the same. The never-able-finish-work is still mountain-height. I doubt that I can ever finish them as what I have promised to myself. I am a useless person. I can never able to do what I have promised to myself.
It has been some time since when I last felt the same lost and hopeless feeling. I am scared… It seems like I am really stupid and useless. I cannot understand what is being taught and I cannot work hard as what I have promised to myself. I am really very frustrated with myself. Just what is wrong with me? I must be sick….. I am totally useless and hopeless…