What we eat can either help us or hinder us, especially when you have a chronic illness like endometriosis. As Hippocrates said:
Here's a great list of vitamins and how they can help endo (so check it out!): http://www.articlesbase.com/womens-health-articles/endometriosis-part-ii-how-to-treat-endometriosis-with-vitamins-1127429.html
And they also have one on minerals (cool!): http://www.articlesbase.com/womens-health-articles/endometriosis-part-x-how-to-treat-endometriosis-with-minerals-1160644.html
About those vitamins and minerals. (note: the below quotes are from http://info.spectracell.com/bid/87780/Nutrient-Correlation-Wheel-on-Estrogen) A good source of information on specific nutrients is World's Healthiest Foods (see http://www.whfoods.com/nutrientstoc.php). Food sources are the best way to get your vitamins and minerals et al, as you get a good combo that often works in tandem for their beneficial effect (one vitamin that helps you absorb/use another are often found together in food!). Taking a pill form can be good, but these should be discussed with your health care practioner first!
Let's take them alphabetically:
B vitamins help convert estrogen to its weaker form (by helping your liver) and convert omega-3's into healthy and helpful prostaglandins (anti inflammatory and relaxes uterine muscle). It particular folate (B9) "regulates estrogen’s effect on genes". B6 has been shown to decrease menstrual pain and "protects genes from estrogen-induced damage thus lowering risk of hormone related cancers; Detoxifies excess estrogen via methylation pathway; Estrogen-based oral contraceptives cause B6 deficiency."