Marcos: Bom dia, doutor. Estou doente.
The doctor is treated with "doutor". Sometimes with the name, but ever with "doutor". ("Doutor Souza").
The regular verb "doer" (to have pain in), is defective. It just exists in two conjugations. Singular (dói) and plural (doem).
Now, it is time to learn some new words:
"Trata com (what) (frequence)" "Treat it with (what) (frequence)"
Frequence = (something)+ (number) + "por" + (intervals)
I do it three times a week = Eu o faço três vezes por semana.
"Tenho/Tens (what)" "I/You have got (what)"
The disease is determined with the verb to have (ter).