These are a few of my symptoms for the last 3 months, body rash including itchy skin, tachycardia, afib, flushed hot feeling running through blood, muscle aches, diarrhea and tenderness below breast bone. what could it be?

Well, there may more: Than one issue. I'm sure your physician has checked multiple labs including the thyroid and electrolytes.The rash is hard to tie to the afib., diarrhea and body heat. Say you have high stress and poor sleep; then menopause sx's. Anxiety can affect bowel and cause rashes. No diagnosis, high stress.Cymbalta (duloxetine) helps anxiety, hot flashes, pain, and a sleep med may help. Treat during w/u, sum sx may imp.

Too many to ananlyze: When a wide range of symptoms, affecting more than one body area occur, endocrine or neurological issues come to mind. I would recommend an internist or an endocrinologist evaluation.

Viral? Hodgikin's?: These are non specific complaints with a broad differential diagnosis. Such as viral infection, hodgkin's lymphoma, thyroid dysfunction, etc. You need a comprehensive work up asap!