Suggest Cure For An Itchy Skin

i have been suffering from itchy skin for the last 6 months. it isnt chronic, but seems to be worse at night, around the time of my period, and when i come inside from the cold. its most itchy on the inside and backs of my thighs, my rear, and around my pubic area. the thing is, there is no rash or dry skin to account for the itch. does anyone have any ideas what this may be? i havent been to the doctors because of the lack of visible signs. i am a female, 21 years old.