Firstly I would advise against using biological washing powder for undies as it can definitely exacerbate the symptoms.
Secondly, always get these symptoms checked out as it could be more serious. I have had Lichen Sclerosis for donkeys years and it has turned cancerous, more than once, resulting in major surgery. Not wanting to scare anyone, but it can be too easy to dismiss symptoms as ageing or the menopause. If you don't want to see your GP, you can attend a walk in at the hospital GUM clinic. They sorted me out. Better safe than sorry.