Today at track i got tired help?

I went to track on friday after missing a week, and after the warmups we were doing 8x100's and well on the 5th i couldnt go on. im not usually a sprinter but ive been able to handle the workouts, i got soo tired that i felt my airway open up to get even more oxygen and i couldnt even do the cooldown lap. what happened to me?? i was getting dizzy and my vision blurry, i have NEVER felt that tired in my life. i was getting headaches earlier in this week, and its been a very depressing, stressfull, lazy week.