Dear mrhea: Often the severe cramping, accompanied by nausea and vomiting, is a result of excessive prostaglandin production. Most menstrual cramps are caused by the release of prostaglandins from the lining of the uterus. Prostaglandins create both the cramps of labor and menstrual cramps by making the uterus contract. Common cramps may start prior to the onset of flow and usually last 72 hours. There are also receptor sites for prostaglandins in the bowel and central nervous system. Thus prostaglandins can produce not just cramps but also nausea/vomiting, diarrhea, headaches, and other "flu-like" symptoms.
In your specific case you also have the known, marked endometriosis ("endo"). Sometimes the endo can even invade the muscular walls of the uterus--this is called adenomyosis. In both instances the pain of menstruation, caused by prostaglandins, is amplified by the pain from the bleeding of the endometriosis implants.
What is most perplexing to me is the precisely every other month (right side only) severity of your pain. Endo implants do not usually act this way. One thing I would wonder is if your uterus is to the right of the midline of your body--or if there are more endo implants on the right side. Some women do seem to have unequal menstrual pain from month to month.MULTIPLE literature searches at the National Library of Medicine site did not yield any useful citations. One journal article from 1984 described a patient with a pelvic mass on the right from a supposed IUD caused infection where pain was erratic.
In terms if the coarse facial hair, one cause MIGHT be increased male hormones ("androgens"), or decreased levels of sex hormone binding protein produced in the liver. One of the common causes of this can be polycystic ovarian syndrome (PCOS). Usually women with PCOS are plagued with irregular/missed periods, acne, unwanted hair growth, and may be overweight. Typically none of these would be likely to cause your pain symptoms.
I would urge you to return to your GYN about the reappearance of the severe pain. They may want to do a trial of one of several types of hormone therapy used to suppress endometriosis to see if this can eliminate the cyclic pain. Gosh, we hope something can be found to give you back your quality of life.
In Sympathy,
Jane