Itchiness all over! What should I do?

About 3 weeks ago I started itching all over with no apparent reason. Its an itch that has affected every part of my body-soles of my feet, hands, even my tongue. I get very red when I itch, too, and the itching usually lasts all day but gets worse at night and first thing in the morning. It also gets worse when I shower. There's no rash, just redness when I itch. I don't have dry skin, or any food allergies that I know of. I haven't changed my detergent in a while, but I stopped using dryer sheets and that didn't help. I've changed my bedding a few times, didn't help. I've tried aveeno products and Benadryl, and neither have helped. What's the next step? I would rather not go to the doctor...is there anything else that I can try to get rid of this itchiness?