HELP!

My son is 2 and yesterday I had to take him to the er and they just said he congested. That he has a upper respiratory infection and try to keep him hydrated. Since Friday I’ve only changed him twice. I’ve tried every way to get him to drink something and he just keep saying no and throwing his cup. I just gave him a nice warm bath but still nothing he’s just been whinnying and kind of breathing hard and just want me to hold him. What should I do?! Do I need to take him back to the er?!