Have you done a search for 'jock itch'? It's a fungal infection which is common 'downstairs' especially in the summer when it's warmer than usual. There are over-the-counter treatments for this. Good luck and feel better!
There are many products available. Go to your pharmacy and look for the athlete's foot products and read the labels. Many of them are also for 'jock itch' and other fungal infections. Look at Tinactin and Lotrimin, but be sure and read the labels and make sure it specifically says it's ok to use in the 'downstairs' area! You may be able to get a generic version of one of these medicines which would be cheaper. If you can't find what you're looking for, don't be shy about asking the pharmacist. They are happy to help out. Feel better soon!