Rough it out. If you keep saying you are sick, you are not going to feel good. Agree that you might not be feeling your best but "dammit, I'm going to get going and get through this". Then force yourself to study in a quiet place void of distractions, really forcing yourself to get into it. Give yourself breaks (set a goal and don't get a break until you meet that goal). Drink plenty of fluids. Kick some ass.