It's difficult to know exactly what kind of scar tissue is there and whether it is just vaginal or also involving the cervix which I suspect it is. The overall symptoms sound as if there is certainly blockage to outflow of the menstrual tract. The net result is retrograde flow or backup of menstrual tissue into the pelvic cavity. This produces endometriosis. We see this with congenital obstruction by birth defects and post surgically sometimes after operations or procedures that occasionally cause scarring of the cervix.
Scar tissue can progress slowly over time and it can get worse.
I don't know of anything that slows down the process. At a young age, all that can be done is to decrease the flow as your doctor has done and surgically dilate the birth canal periodically. Dilatations for cervical stenosis only last for about 3-12 months. My doctor has suggested vaginoplasty. I guess the MRI I had done showed that the scarring was only in my vagina, but it was 6cm in length.