I Have A Itchy Skin Rash All Over My Body

I have a itchy skin rash all over my body for over a month now. It seems to itch in two's . . Both sides of abs , both sides at the same time, behind the knees both at the same time, inside the legs both legs at the same time, cheeks of buns , left and right, at the same time . I scratch till it bleeds and still is itchy. Can occur at different time of day and more often in evening and nightime. I have small pimples or spots all over my body , including my back.