Very sick today, Sunday

Another terrible day of vomiting. I know he is getting dehydrated again. Only got a light breakfast down and has been vomiting all day. He does not want to go back to the hospital and I don't blame him. I will have to see if we can get a home health nurse out tomorrow to give him IV fluids.
It is horrible to watch him get so wrenchingly sick.
Why did the vomiting stay under control for 3 days and then back to it again? We are not doing anything different. Why hasn't the meds worked the last 2 days? He cannot even talk he is so nauseated. I am having trouble coping with this and not knowing what to do for him.