Itchy Rash On The Chest, Back Post Hysterectomy, No Improvement With Benedryl, Z Pack, All Tests Normal, Slight Elevation In WBC

I had a hysterectomy almost 4 weeks ago, about 5 days after surgery I developed a pimple looking rash , doctor took me off cleocin and put me on benedryl . did not work. I went to family doctor thought I had pneumonia due to cough, so put me on a z pack and said should help with rash also, did sttle down some. Rash is back all over my chest(which is the worst), back and some on my arms. Never had other than a few pimples here or there on my neck before surgery what should I do and what could it be. Has become a little itchy. family also did blood work WBC normal, liver enzymes normal, CBC before and after surgery normal other than slightly high WBC post op