Hi, I've had sheep flukes and no doubt, probably also have the same as you in my uteris.. as whenever I would get my period, I sometimes would find similar in the toilet bowl after urinating. I do believe that the conditions during menstruation do kill some of them due to "changes in their environment" as you stated.
What I would do is check out Dr. Hulda Clark 's writings on fluke worm.. Seems that she found that when we are continuously exposed to solvents (acetone, non-food grade alcohol, and various metals, etc) that it causes our bodies to become more vulnerable to parasites.. fluke being the most common.
I would periodically continue detoxing with her cleanses...as well as sticking with an alkalizing plant based nutrient rich diet to keep the immune system strong.., and not skipping on eating fish, tuna, salmon which are known to boost uterine health (which ties in with the endometriosis. (In fact, whenever I got my period, my body would CRAVE salmon or tuna)
Get your healthy oils, and make a point to do a twice a year (at least) parasite cleanse with anti- parasite herbs.. Fluke worms hate oregano oil.