I Have Had A Itchy Rash Since Last Summer Starting

I have had a itchy rash since last summer starting on my chest which is very very itchy and has spread to my arms, legs and back. I have small bumps in some areas and some blisters. I am Celiac but my GP and Dermatologist cannot diagnose and are sending me to a rheumatologist because they think it will be autoimmune. I will not see the rheumatologist for a few weeks. My skin becomes very very red if I scratch my legs and I try so hard not to scratch but it is so difficult. I am hoping that perhaps you can help and I would be so grateful. Thanks