Diseased implies you are ill; in-which consulting the good doctor sky or making some medicine is the only thing that can cure you. Though be warned that if you are knocked out via the disease you will die. Try taking five doses of each medicine if no predominate effects are in place yet as taking a shotgun route to curing yourself early on will cost less resources than later on when the disease if fully grown.
Try willow bark tonic. Made via boiling willow bark. You'll receive soaked bark and a pot filled with willow bark tonic. Drink it via making a bark cup and filling the cup with the tonic; thereafter equipping the cup and right clicking to drink it.
Try columbine paste. Made via grinding wild columbine, 0.5L water, and myrtle oak leaves in a grindstone.
Try smelling salts. Made via grinding antlers in a grindstone.
Try using a leech. Apply leech to your shirt slot and allow to become bloated. Each feeding it has the ability to cure your disease.
You may find yourself with symptoms of one disease and have the complete opposite; thus is why trying everything is recommended.
Alternatively you can add the good doctor via the hearth secret: Doctor Sky
This is good folk and will cure you free of charge and teach you how to protect yourself. To prevent future disease buy a plague doctor's mask, or the store version, and wear it when encountering any folk in the main town.
Consult this thread to further your education of disease in Providence:
viewtopic.php?f=21&t=11797Best wishes.
-Mr. Bellflower
Keep calm and stay peachy.