Nine year old-random vomiting

Hey! So-on Sunday morning, my nine year old started saying his stomach hurt, and by 1, he was vomiting. He continued vomiting until that night. He was still weak on Monday, but no more vomit, and by yesterday he felt like himself again. Eating, playing, etc. I thought we were in the clear. Then, around 5am today, he started vomiting again. It’s 9:30 now, he hasn’t vomited since 6, and he seems to feel better. He’s not “sick” like he was on Sunday, if that makes sense? Sunday he was weak, and needed to lay down. Today, he’s himself other than the vomit. (So far) The two day break in sickness, plus the fact that no one else in the family is showing signs of a virus-makes me wonder if it’s environmental? So I started thinking about what he’s been eating. Both times, he had a sandwich from chick fil a. We eat CFA often, and have never had any issues. Plus, both nights that he ate it, the rest of us did too, and again-no issues. Is it possible that he’s developed some sort of adverse reaction to it, seemingly over night? He was this way as a toddler, too, and it ended up being chicken nuggets. Not even kidding, Tyson. Does he just have a random allergy to chicken?? Bluh. Any experience or thoughts welcome! I’m talking to his pediatrician as well, just thought I’d reach out to my mom community too!