My son is 5, and since he could crawl, he has been doing what we call "rocking". He will lay down with his hand under his penis (with clothes on) and, basically, hump the ground. We have also caught him doing it in the bathtube just after letting the water drain from the tub. Is this a normal developmental thing? I have explained to him, that it is a private thing, and that he can do it in private. I dont want to teach him that it is wrong of dirty, although other parents have scolded me for that. Am I doing something wrong? How should I react? He has done it since babyhood...is it a sign of sexual abuse?