Welcome to HCM.
It seems to be hair route infection after shaving and intercourse.
Most likely it is mix infection.It might be due to scratching after perspiration and sex.
You have to take proper local care.Use medicated soap to clean.Keep that area dry.Avoid sex till get complete cure.Avoid unprotected sex.Don't wear tight undergarment
Apply anti fungal,antibacterial and steroid
gel/cream will be helpful.
Start oral antibiotic like oflox/ornidazole
and anti fungal like flucanazole 150 under guidance of your doctor.