I Went To My Dermatologist Last Tuesday With Severe Itching

I went to my dermatologist last Tuesday with severe itching on my head (that was going on for over 5 weeks). Then it spread to my entire back/buttocks. She said it was contact dermatitis and gave me Clobetasol cream for my back and in liquid form for my head. After 5 days using 2x a day the rash has spread to my arms, stomach, breasts, and ears! I believe it is something else-maybe scabies or bed bugs because my sheets, and mattress covers all had either small black specks or red specks that I could see with a magnifying glass. It is the 3 day Memorial weekend so no docs are available. I considered going to the ER but I know it will be so expensive. I have decided to stop the meds that are not working and treat the itch with Sarna lotion and take Benadryl before bed. I also find that cold cloths feel great but that limits my activity and I work retail-lots of nights and weekends! What tests are performed for accurate diagnosis?