There is no proven way to reduce the risk of endometriosis, though there are some theories out there. Women who have children early in life seem to be at less of a risk, because when you are pregnant you don’t menstruate. Similarly, women who use the pill for long periods of time and have light periods may minimise the amount of blood flowing back. But there is no objective evidence about these theories.
If you have pelvic pain or bad period pain and suspect you may have endometriosis, you should seek medical advice. It is better to have it diagnosed and treated earlier rather than later.