Kidney Pains

I am on my fourth day of MC, but since yesterday I have been getting really bad lower back pains in the buttocks kidney area. Also I had nausea this morning. I don´t do the SWF (Salt-Water-Flush) but I have Senna tea in the morning and at night, which is working well for me.This is my second attempt at MC, the first time I gave up on day 4, this time its been really good except for this back pain. Can anybody help me? Should I stop? Is this normal?