Prominently itching spots in the genital area raises several possibilities, including jock itch, yeast infection
, scabies, crab lice, allergic reaction, and others. But unlikely to be herpes, syphilis, or other classical STDs. If it's a fungal (yeast) infection or jock itch, the hydrocortisone will make it worse.
Bottom line: Stop trying to guess and to get a diagnosis on line; see a health care provider.