I hear you. With me it's usually when I've done a little - and I mean a little - extra with my body, such as carrying an object that weighs a pound or two for a few extra yards. No, I'm not kidding. (That one thing may not tip the balance on any given day, but if I add, say, walking around 2 stores for a few minutes instead of just one, I know I may well feel like I'm getting sick the whole next day. Or it might not hit until two days later.) My doctor said, years ago when I told him this, "Yeah, it happens, and we don't know why.
Not a big help!
It's very frustrating when we have the desire to do normal things and always have to pay for them.
At least we're not alone, though it often feels that way.
Nice to meet you.