I've Had A Horribly Itch Rash On Seemingly Unrelated Parts

I've had a horribly itch rash on seemingly unrelated parts of my body for months. It started on my eyelids (both eyes, but generally not at the same time), then moved to my forearms (both) near the elbow, then my butt crack. It would seem to cycle through these areas (arms itch for a few days, eyes and butt are fine. Then butt itches and arms and eyes are fine, etc.) I saw my doctor about a month ago and he prescribed a steroid for 9 days. It seemed to lessen after that, but didn't completely go away and is back worse than before. Now my ears and scalp itch as well and the rash is simultaneously irritating my eyes and butt ( arms have been fine for the last few days). I am frustrated and uncomfortable, and my doctor didn't seem to have a clue as to what it could be. Please help!