Did they do a CT scan? With the fast heart rate, they really should be checking you for a pulmonary embolism. Not being able to keep down water, with diarrhea and vomiting, it is definitely concerning and may point to a blockage or stricture.
I agree with @catwoman7, you might want to get back to the ER.
Of note, I had diarrhea the ENTIRE time I was on liquids - so I'm not surprised there. But, I only had vomiting for a day or two after surgery.