Hello!
I believe your body's hormones are trying to regulate and the discharge you see is it's attempts at period bleeding...being that you have gum problems and poor appetite are trying to tell you you may be anemic and probably lacking some very important minerals...Are you taking a good daily vitamin? One with 500+ mg of vitamin C? (Vitamin C helps iron to absorb into the blood)...If possible, drink fruit juices or veggie juices instead of sodas, things like beef jerky, nuts and trail mix instead of chips...These have loads of easy to munch good stuff in them, and will give you longer lasting energy and be better for your body...It would be a very good idea to have a simple blood test done...it would give you a better idea on what is going on...
Most women after having their periods for the week get that dark brownish blackish discharge you speak of as your blood is older and starts to color. When your menstrual cycle normally starts the blood should be bright red and then during the end of the week it turns the dark color. I cannot remember getting this before I had my period, but your mom should take you to the doctor to rule out anything. Since you have not started your period I cannot see you having an issue with iron deficency which can cause the low energy. The pain can certianly be caused by your period even though you may not have it yet. I know that I will have abdominal cramps even before my period starts.
Again, have your mom take you to see your doctor to rule anything out.
Good luck.