Suggest Remedy For Rashes In Genital Area

I am 24 years old, weigh 200lbs, and am 5'5". I have had unprotected sex since I was 14, but only with 6 different men. I noticed from the first time I've ever had sex, I'd start having rash in my private area, but it would go away a few days later. It's an on & off thing. Now, I still have rash, but it is worse. It's spreading to my bottom & between my thighs. It's hot, red, itchy rash. I don't want to scratch it, but I can't help it because it's irritable!! I feel all of my scratching has made it look worse! What should I do? Do you have an idea of what's going on with me?