Suggest Treatment For Itching In Legs And Waist Line

sir/mam, i m 29, 5'8", 72kg...suffering from severe itches in my underlegs part and in the center back side of waist line. i googled and it seems that its jock itch. i have stoped using undergarments and so there is a little relief but i want to cure it. its complete discomfort bcos of that. the area where i get itches, turned black. though some part is becoming normal since i have started taking precautions. i hv observed that many a times, i do suffer from zit/pustule/papule after i finish my office work, probably due to sitting on raxine chair. i dont know its bcos of jock itch or not. the skin gets normal after 1.5-2 hours. pls help me....by suggesting me treatment/cream for that, and how can i prevent/avoid it. thanks