Dog digestive upset

Question
I have a 5 lb. min-pin mix. She has recently recovered from an abscess that developed at the site of a rabies vaccine injection. She was on an antibiotic for 12 days which I stopped giving her last Saturday when the scab fell off. She vomited Sunday, mostly yellow and small undigested bits. Monday she developed severe liquid stool which continues today and now has a few drops of blood in it. She is still active and has not lost her appetite, but I am worried.

Answer
My question to you is this Jennifer: what were you giving the antibiotics in? Was it a little piece of ham one day, cheese the next?

The point I am getting at is that little 'surprises' like that can really upset a dog's stomach and can even cause pancreatitis. That can be very serious and will cause vomiting and diarrhea.

This could be related to the antibiotics but it is a bit late for that to be the cause. The blood is from her rectal tissues being irritated from the diarrhea.
I would call your vet tomorrow if she is still vomiting.