My legs itch so bad that I'm scratching skin off...?

I've been having this issue for years. Its worst at night and generally below the knee. Its such a bad itch that I can't get it to go away. I literally have to dig my nails into my skin before it goes away and then its only replaced with pain. And worse, if I don't scratch them then I have uncontrollable twitching of my legs from the thigh down. Its ridiculous and nagging and I want it tto stop. Doctor says its just dry skin but there's no way, I've tried exfoliating and applying creme, I've tried an steriod for eczema. Nothing is helpinggg help me its driving me crazy