There are a lot of things that can cause itching. Of course keep trying your doctor -- don't give up!
Here are a few things that can cause itching:
* allergies - could be food-related or something like changing your brand of fabric softener
* skin irritation - again, could be caused by new fabric softener, also by rough clothes, like wool
* healing wounds - and you can perpetuate this by continuing to scratch, and thereby reopen the wounds. It can be maddening, and very hard to stop (I've been there, I do understand)
* dry skin
* fungal infections
* bug bites - have you checked for things like bedbugs?
* hypothyroidism (low thyroid, but you'd most likely have other symptoms, like thinning hair and eyebrows, and more difficulty losing weight)
* body lice
See here for more info: http://www.medicinenet.com/itch/article.htm
And keep trying to reach your doctor!