Will my Professor tolerate this medical excuse again? A week ago In one of my classes I e-mail the professor and asked to reschedule one of my quizzes due to illness generated from sleep deprivation, she accepted and was highly considerate of my situation.

Now, due to my intense anxiety &amp; stress of exams (to perform excellently) and lack of sleep for the last couple of days as well, my body is failing me and now I woke up to dizziness (fainting/falling sensation), fluctuating irregular heartbeat, and confusing feeling I can't focus on my work at all... 

I'm going to the clinic as soon as it opens in a few hours and the exam is also in a few hours, I feel as if the professor will not believe me but as I visit the clinic to be sure this is not serious, I will ask for a medical note. Will my professor tolerate this again? In our syllabus an exam can be re-scheduled for medical emergencies. I believe this is a medical concern. 

I maxed out my body for school too much, trying to do well and sleeping less (creating "more time").

Bear with the writing, I'm not in a perfect mental state...
Go to the hospital NOW and worry about the exam and your professor later.

If you tell your professor that you had to go to the hospital, she'll most likely just accept that. Of course, you can ask for that note nevertheless, just in case. 

Once you are ok again, think about how you can reduce stress and get enough sleep regularly. On the long run, constant lack of sleep and stress will hurt you (even more than it already did so far).