What Could Itchy, Spreading, Discolored Rash On Stomach Be?

I have had a rash that started in my groin area that started 9 months ago, it iched bad, I used anti itch cream and the rash has mellowed out but the skin has turned a dark color,the rash has moved up to my stomach just under the belly where it is still giving me problems, It has also moved under and up the crack of my butt, where again it has turned a dark color...can go day's without scraching then all of a sudden I just go to town scraching.My wife also has a small patch on her leg west of her vagina. Have no health ins. and am on disability and can't afford to see a doc. is this somekind of std? I am 49 years old,Married,I am 6' 5" 285 lbs. I smoke,drink beer, I have had a quad. heart bypass, I have had a gastric bypass, Had diabetes until I went under 300 lbs. Both parent died from cancer. I have sleep apnea...I am vitamin B dephichant which I hav'nt had a shot in over three years...Itch is driving me crazy....Any home remedy you can help me with?