Your dog pooping out blood

This is happening to my dog too. She is sick, lethargic, has wheezy breathing, pain, vomiting, and deep red bloody stools, of which are more blood than stool. She also won't eat, or drink anything and hasn't in 2 days. We have been forcing water with a syringe. The vet gave us antibiotics that don't really seem to be working, but they ran a bunch of test, all were negative. I think she is dying. Can anyone help please? Has anyone has anything like this happen to their companions?