I'm not sure what this black discharge is. Are you sure that this black material is from your vagina? Sometimes old blood either from the vagina or rectum can appear black. From your description of the oily appearance and that you vomited up dark material, it sounds like the blood is most likely coming from your gastrointestinal (GI) system not from your vagina. It might be that you are bleeding from your stomach or some where else from your gastrointestinal system (stomach, intestine, colon, etc.), and some of it is being vomited up and some of it is coming out the other end.
I would definitely go see a doctor soon, like in the next week to figure out what this is. If you are bleeding from your GI system it is very serious and can cause anemia and can be life threatening if the bleed becomes more aggressive. Most cities have free clinics or low cost clinics for people who don't have insurance. I would perhaps either look around the internet to see if you can locate on near you or call the closest public health department office and ask them. But you definitely need to be seen by the doctor
honey go to the doctor and eat the bill later that sounds serious