help, my one year old keeps touching herself

Help please, is this normal, over this last say, month, my 15 month old daughter keeps touching herself inappropriately. It started off when I was changing her bum, she would get the hands down and start feeling about. But now, it's every chance she can get, even just getting up, sitting on the sofa and sticking her hand in the side of her nappy. And she literally sticks her fingers right into herself. It makes me feel sick, and worried. But all the same I can't put it down to being abused, because she never leaves my side. Lol. Her dad is around etc yes. But he's always working flat out so would very very rarley be alone with her. Not that I'd ever think he would anyway. So I'm wondering, is it just normal behaviour?