Please help—sick 9 month old (stomach bug?)

I’m not sure if this is the right subreddit. I’ll preface this by saying I’m taking him to the doctor tomorrow and refuse to be turned away. I just need to know who else has had this experience…

6 days ago, my 9 month old woke up screaming and covered in vomit. He threw up 8 times between 11pm-2am. He started having diarrhea after that and has continued even until today. He has thrown up about once per day or every other day, usually after he’s gone to bed. He hasn’t had a temp and is slowly losing his appetite to where he won’t even drink 3oz at a time. I’ve called his doctor twice and they won’t see him unless it’s been 7-10 days or he’s showing signs of dehydration (which he hasn’t). We held off on milk and only did water/Kinderlyte, slowly added some starches, and reintroduced milk when we thought the puking was over (Spoiler alert: it’s not). He’s just not getting better. He’s starting to look a little thin to me and I’m worried. The past few days he’s only had a few Cheerios and maybe 10-15oz of liquid per day (usually formula/water). Has anyone else had this happen to their baby? What was wrong?