I suffer from severe rective hypoglycemia. I want to know what to do regarding fast days. Thank you.

As with all medical questions, first consult a medical doctor as to what he believes is necessary, what the consequences of fasting would be, and if total fasting is a danger- then how often and how much you must ingest over the fast etc. Afterwards, with this information, consult (or have your doctor consult) a rabbi.