Should probably ask your doctor...
Brenda640, I think this needs a medical evaluation (as maw mentioned) because it could be serious.
It is likely hematemesis ( vomiting blood) due to G/I
damage or other internal trauma.
When blood mixes with certain enzymes in the stomach, its color changes to dark.
Unless you had been eating a huge quantity of black licorice or dark chocolate, I don't personally know of any other possibility.
Please note that my comments do not constitute medical advice.