I have been up all night cramming for a final exam. At about 8 AM I go to the donut store and get a super size?

I have been up all night cramming for a final exam. At about 8 AM I go to the donut store and get a super size extra strong coffee and 2 donuts. At about 10 AM I start getting very irritable, develop a pounding headache and get lightheaded. Using a combination of what you have been exposed to this past semester, speculate why this may be happening.