lets just say Its a 50/50 chance that the Torah is divine ( even though it takes a couple of minutes to show anyone that the Torah is G-d given.
If I am right that the Torah is divine then you will get Kares if you do not fast Yom Kippur. If on the other hand you are right but you listend to the Torah all you lost is a day of not eating.
So in simple terms for a smart calculated decision it is pretty clear you have nothing to loose and everything to gain by fasting.
And beg G-d to send you the correct guidence. The worst sickness a person could have is that he doesnt even realize that he is sick
Hashem yerache alecha val kol yotzei chalothecha I bench you with a gut yar !