You had not mentioned your age.
Whether you are having diabetes
It is probably due Intertrigo
, a form of eczema, occurring usually moist warm area. As you have vulvitis
and vulvo-crural folds involved, it is probably due to intertrigo. It may super added with yeast or other fungal infection
. Repeated scratching will produce secondary bacterial infection and subsequently painful intercourse.
You approach a Dermato venereologist, they will fix the diagnosis and treat accordingly. It is not very difficult to treat.
Get well soon.