I am 60, overweight, no uterus, have ovaries; have small amount of dark vaginal discharge

I had a partial hysterectomy about 20 years ago. I still have my ovaries. I haven't been to a dr. in 6 years except for a mammogram & colonoscopy. I am experiencing a small amount of dark vaginal discharge - 2x in the past week. I had this 2x last year at widely separated times. I am married to the same man for 41 years and have not had sex with anyone else in that time. The discharge seems to happen during the night. I have not had sex in a week. I have CFS & Fibro otherwise I am in good health except that I am obese. I don't have any abdominal discomfort. My back is hurting, but that is not unusual. I've been a little more tired this week than in the past few weeks, but again, that is not unusual. Can someone please give me some advice? Thank you.