I have an intense rash on my buttocks, with dark skin discoloration what is it?

[unknownz86]

so I've had this condition for over a year, havent been able to afford to see a doctor. The itch gets worse in the evenings/nighttime. The area that itches starts at my upper thighs and goes almost  all the way up my buttocks. I originally thought it was a really bad heat rash, but it wont go away. I treated myself for pinworms at one point thinking that was what was wrong, but the itch persists. Only recently (to my knowledge) has the discoloration occured. I just wanna know what this could possibly be.

[Paxiled]

You're going to have to see a doctor.  Why is it you can't afford one?  If you're truly poor, the ACA if you're in the US allows for subsidized insurance.  Most places have clinics that serve the poor.  You're not going to get diagnosed over the internet for something like that.