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.
Good luck-- HHH, MD
HHH, MD