Be sure to follow the proper diet while doing a liver cleanse. There is an effective one here.

Are you on a good anti-parasitic? 99% of people have parasites now because of so many toxic substances in our air, water, food supply and off the doctor's prescription pad. Toxic substances are poisons and depress our immune systems, kill body cells and pave the way for parasitic infestation.
What you are feeling and how your body is responding seems normal to me while doing a cleanse. You're stirring the toxins up and brain fog is the result. You've started, and now need to continue with the anti-parasitic, clean out your colon and do some liver flushes, IMO. Not only the parasites must be killed off and eliminated, the poisons have to be eliminated, too. People in general, stop way too soon for their bodes to get the stuff eliminated and for their bodies to return to homeostasis. Liver, colon, blood lymph and tissues must eliminate the poisons and parasites--in that order--for the body to get well. Just take it a little further and I am sure your body will recover. Poisons screw up the hormones, if your monthly cycle is affected, so getting rid of the poisons is just a little longer trip than you anticipated. You're doing OK, just take it a little further and follow how the body works getting rid of those poisons in that order, and I feel you can accomplish your goal. I did.

I agree with bugrally. The way that your liver dumps toxic substances built up over time is through the release of bile. Your digestive system is likely reabsorbing the toxins, which is contributing to your symptoms. You could take it slow to see if it gets better or worse, but speeding the process up, by doing a Liver Flush for example, might prevent your body from reabsorbing toxins.