Guys, I'm better now, or at least haven't had any problems since yesterday. Even better, I may have found what caused the thing. I was suspicious about it having to do with my mountain vacation, since the other 11 people didn't get sick. Anyway, you know how pyrat recommended me yogurt? Well, I had a 4-pack of vanilla yogurt, one cup of which I had Friday when I got back, and another that I had when I was recovering Sunday, before getting sick again Monday. I go back just now for the third cup, and lo and behold, I spot on the packaging, the expiration date, March 28, 2021. Good thing I didn't actually open the third cup. Both third and fourth cup are in the trash now.
I mean, these groceries were bought for me on April 6th, so those shouldn't have been in there anyway, but I will have to keep a better eye out. But yeah, eating March 28th yogurt on April 9th and 11th, probably not a good idea.