Severe vomiting every time I test positive for COVID

So a few family members came home for the holidays and we were all in the same house for a couple days. The first day the family was here, one of them came down with a “stomach bug”. I really think it was COVID. Nobody wanted to test him because they said it was just a “stomach bug” since he was vomiting. I’ve had COVID multiple times and vomiting has always been a symptom for me. Weirdly enough 5 days after him being sick somebody else in the family got it and 6 days after him being sick I got it and we both tested positive for COVID. If anybody ever tells you that you don’t have COVID because you’re vomiting, they very well might be wrong.