Plz help.. Need Advice about fasting

Hello every one i live in place its hard to find doctor who agree for water fasting... I always read and see if u want do long fast u have to be under doctor supervision... So dose any one try fasting under doctor supervision? What will doctor will check every day in body other blood Sugar and blood pressure?? By the way im asking for fasting over 20 days.. Before i did 14 days and i felt pain on front ribs after any effort i do

Thanks in advance