Don't worry...you are suffering frictional dermatitis causing this problem... Specific medicine available for good control... Treatment depends on the severity..Do direct online consultation for detailed prescription

I think u need to avoid the habit of folding legs at any time. Take care that u don't put any kind of pressure or friction to these areas which would make it more worse. Do take a proper consultation to treat u for the same.

Hello ! You are right , the rash has developed over areas where there is constant friction and rubbing due to sitting in the same position. The skin has tendency to thicken in such areas and appears darker. To avoid further thickening avoid sitting in position that would but your body weight on these areas , keep changing position of legs , avoid scratching as much as possible and keep the area moisturised- use a moisturiser2-3 times a day . Also , always better to use a moisturiser immediately post shower as the skin is wet and soaks in better .