The last couple of months, I feel tired all the time. I sleep at least 9 hours a day, even more sometimes, but I still wake up feeling exhausted. The last couple of weeks I noticed that my stool is a dark grey colour. My energy level sucks for most of the day but I've continued to stick out to my work out routine. I run a couple times a week, play tennis, and do light weight lifting. I drink alot of water, take my daily vitamins, and eat fairly healthy. And i'm only 22 years old.
I went to the walk-in clinic last week and the doctor said he felt some inflammation in my stomach and wanted for me to come back next week. I decided however to book an appointment with my family doctor, but I wont be able to see her for another couple weeks. My menstaural cycle has stayed normal, and I am not sexual activite right now.

So im just wondering what possibly could be the causes of these symptoms?