Fasting doesn't damage your body. The only real sign to end a fast is real hunger. The only other 'danger' periods are healing crises which you shouldn't end a fast on unless you have no choice in the matter- such as your needing to keep working for example. Otherwise you are better off continuing a fast in almost all other cases than stopping because things are getting a bit hairy.
The only other reason you should end a fast is fear. If you become afraid a symptom will do you serious damage and nothing will allay your fear then it is safest to end the fast correctly. But in my opinion you should NOT go to a normal doctor in this case. The only doctors qualified to diagnose you while fasting are those doctors already experienced in fasting. If you go to a 'normal' doctor while fasting you are risking serious harm to your body in relying on their ignorant diagnosis and treatment. Again I add the disclaimer that this is my opinion. ;)