Hi. I haven't ever taken Yasmin, but before I knew I could have Endo I was taking the pill (Microgynon30). Since I started taking it I started getting abdominal pains throughout the month and terrible pains during my period, which is the reason I went to the doctor to start with.
Since then I have been put on a lower estrogen dose pill (Loette), which has really helped a lot with all symptoms. Occasionally I still have sharp pains, etc, but a lot less than before.
I guess, since the pills have estrogen in them, it makes sense that it may actually have a reverse effect on endo and actually stimulate activity on the lesion, rather than act for treatment.
I hope this can help at least in the slightest.