Welcome! I am Dr. Altman, a licensed veterinarian and happy to answer your questions today.
I am so very sorry to hear that your little Firecracker is having changes to his stool and vomiting
Because of his size I would be more inclined to have him seen sooner rather than later. Even though he is not actively bleeding
the black stool indicates stomach
bleeding whereas the red blood indicates colonic inflammation and bleeding.
In addition, the trembling worries me because it tells me he is not feeling well. Similar to the chills in a person when they don't feel well.
If he were a large breed dog I would be more inclined to watch and wait but with a little guy like him I would advise the veterinary exam, get him started on appropriate medication so that you do not end up at the veterinary er overnight and he can begin to heal.
What can happen is hemorrhagic gastroenteritis if not treated:
I hope this information makes sense but please let me know how else I can assist you both today. I truly hope he is feeling better soon!
If you have more questions or if I can help in any other way, please do not hesitate to ask! If you would like to accept my answer, please press RATE OUR CONVERSATION (I am not compensated in any other way). Bonuses are always welcome. Thanks!
If you have additional questions after you rate the question, you are welcome to request me for additional conversations if I am on-line or by beginning your question "Dr. Altman..." or "Dogdoc4u..." and others will leave the questions for me. Good luck to you both!!!