That is just all of the negative energy and curses being removed. It is a common feeling. All the negative energy that has been deep inside, is being brought up to the surface, and is being removed. And when it comes up to the surface, it feels worse and stronger. This is a common feeling, and it is a good sign that everything is working correctly. You just need to do more of the Final Ritual. You have to do it every day, and you should do it multiple times every day.