Larry6905,
I'm sorry for the anxiety you are feeling. Unfortunately, that's part of the deal with what you are going through.
It's really hard to tell what's going on, because we don't have your medical history to refer to. Steroids can cause digestive issues and there could be interactions with other meds if you are taking any. It could just be the stress you are under.
If I may suggest, make sure all prescriptions are from the same pharmacy and use the pharmacist as a resource. I was fortunate because my father has been a pharmacist all my life. There are some websites that allow you to enter all meds and it highlights any issues. Make sure your doctors know all medicines,mover the counter products and herbal/natural products as well.
As far as the junk you are hacking up, it could be anything. Even partially digested blood could be black and smell.
Try hard to not let the mind wander into all the "what ifs". There's going to be a lot going on for a while.
Hang in there, we are all here to walk with you through this. Best wishes for some smooth sailing.