I have a sore mouth, my gums hurt & i have a black line on the gums at the base of the teeth, what could this mean ?

Varies: Could be a sign of lead poisoning. You often get a bluish line (burton's line). But likely a more benign problem. Might be best to see your dentist.

Gum disease: Sounds like generalized inflammation of the periodontal (gum) tissue. I suggest you see your dentist for an evaluation as soon as possible.

Calculus: The black line at the base of the tooth could be from deposits hiding under the gum line.This is causing gum disease, you should see a dentist for proper evaluation and treatment.