At the end of the day nothing is 100% especially with cfsme. Everything is trial and error. Sorry can't give u a straight answer. I mostly go off my personal experience as well as what I have heard from others. Testing seems to also be just a guide as well. As for feeling bad after taking famir again it's hard to say if it's a positive or negative thing but in general a healthy person wouldn'thave any reaction to famvir? But it sseems common amongst us cfsers and for some a sign it's stirring up the little buggers.