What Causes Itchy Rashes On Legs?

I have had an itchy rash on my legs, mostly lower, for the last three years. I have seen three different Dermatologolists, but nobody has been able to pinpoint what I have. The last few days my arms have started itching the same way that my legs started out itching. I have little whelps at first from itching and when that goes away there are little pink spots with a lot of itching. I have had nine squamous cell carcinomas. Excuse being tanning bed. I don't think this is true because I always have severe achy joints and slight fever with fatigue when the rash breaks out. The rash on my legs is so bad that I cannot shave my legs. I really need help in getting a diagnosis. Thanks!!! Lisa