I teach on-line classes on medical history before 1840 and Georgian and Regency military medicine. As a result, I've read a number of books on medical history. Below are some books to help get you started on your historical medicine research for your historical fiction.
A Field Guide to Germs Wayne Biddle
Scurvy: How a Surgeon,A Mariner and a Gentleman Solved the Greatest Medical Mystery of the Age of Sail Stephen R. Brown
Captain of Death: The Story of Tuberculosis Thomas M Daniel
The Worst of Evils: The Fight Against Pain Thomas Dormandy
Doctors on Horesback: Pioneers of American Medicine James Thomas Flexner
Western Medicine: An Illustrated History Irvine Loudon
Military Medicine:From Ancient Times to the 21st Century Jack Edward McCallum
Blood & Guts: A Short History of Medicine Roy Porter
Revolutionary Medicine 1700-1800 Keith C Wilbure M.D.