My stool is very, very dark brown and my heart is beating very fast. - #10394

Hello, I am a 16-year-old girl and I have some health concerns that I want to describe. Recently, I noticed that my stool has been very dark, almost black in some areas, but mostly very dark brown. It happened yesterday and also today. I am not sure if it is normal, and it worries me a lot. I have no pain in my stomach, no nausea, no vomiting, and I feel otherwise okay physically. The stool is not sticky or shiny like tar, and I do not have any blood that I can see. I also feel very hungry all the time, even after eating recently. Two days ago, I could go for more than six hours without eating, but now I get hungry very quickly. I have eaten chocolate, fast food from McDonald’s, bubble tea, and beets recently. I also take some sachets for gut health, but I do not take them every day. Additionally, today I have a mild headache and my heart feels like it is beating very fast. I feel a bit anxious and scared about these symptoms. I do not have dizziness, fainting, or weakness. I am not currently on any medications other than the gut sachets. I am worried because I have never experienced these symptoms before, and I do not know if they are serious. I would like to know if these symptoms are normal or if I need to see a doctor. I am looking for advice on whether I should be concerned and what steps I should take to feel better. Thank you for your help.