9 month old stomach bug?

Wednesday i took my son to the doctor because he was throwing up and had diarrhea, she said as long as he pees every 18 hours he’s fine. Well it’s Sunday almost Monday now and he’s been Perot once a day and had water diarrhea and throwing up everytime he ate. He’s had 2 bottles and threw it all up. He ate some pedialyte but thats not enough.. he’s only peed twice today. The doctor said she wants to avoid him going to the er bc of the flu outbreak but he’s miserable and can’t sleep and can’t eat and i don’t want him to get dehydrated. He has no fever... what do i do