The UK's Endometriosis charity, with one of the most comprehensive and user friendly sites out there in terms of info and seeking help for Endo symptoms, diagnoses, treatment and support. My go to and one of my best website friends.
NICE (National Institute for Health and Care Excellence) introduced their guidance for Endometriosis in September 2017. This is a great step in ensuring GPs (and other doctors) are aware of the disease and have set procedures to follow when dealing with it. I refer to it when looking to understand my consultants decisions and treatment paths. It's a great tool to have on side as a patient, too. Start here: www.nice.org.uk/guidance/ng73
Endometriosis UK Support Groups
I am a member of the Endometriosis UK London Support Group. This support group has changed my life. The group meets monthly and has a Facebook group.
If you're not based in London, find an Endometriosis UK Support Group near you.