This sounds a bit like what happens with some individuals who are suffering from candida. Zapping just one day and stopping is not good. Also, there are several things that you need to do such as replenishing your normal intestinal flora, etc.
Also, if you do have a candida problem, the $10 zapper might not be strong enough.
It might be very beneficial to read a copy of " parasite Zapping and the Zapper".