What Causes Dark Stool, Fever And Lower Abdominal Pain Post Partial Hysterectomy?

I am post partial hysterectomy 3-4 years. I still have my ovaries and cervix (almost 100% sure) I have had periodic bleeding (some heavier then other times) I have been feeling ill lately. Extreme loss of energy and stool a lot darker then usual. No change in my diet either. Low grade fever ....periodic lower abdomen pain .....just not myself. Fatigue. Today I saw spotting like a lite period. I am 48