I am experiencing lower-mid bak pain for months now, also i have tarry stools. and i feel tired and fatigued all the time.

Tarry stools: Reporting "tarry stools" to a doctor is like waving proverbial red flag in front of bull. In other words, "tarry stools" is never a good thing, especially when linked to low-mid back pain for months plus feeling tired & fatigued (most likely from anemia resulting from "tarry stools"). Bottom line: go see your doctor immediately. You need egd (upper endoscopy) & colonoscopy as well as cbc, etc.