What Causes Nausea After Periods?

For the past 2 periods the day after it ends in the mid morning I feel nausea and then vomit once and then I feel fine. I am 31 years old and until October of last year had always had semi normal cycles, but in Oct last year I had an ectopic which ruptured my left fallopian tube. After emergency surgery to remove the pregnancy and tube (they left the ovary in for hormones) I now seem to ovulate on the full moon and my period starts 5 days after that and is light and only lasts 3 days. I know I have a tipped uterus that tips way back to my spine, the ectopic actually happened because my left tube was tangled in a crease in my colon so diarrhea and painfull cramps are normal before and during my period and I have always been borderline anaemic. Why am I suddenly having the vomiting the day after period stops?