To be, or to feel under the weather is a common idiom used when you are not feeling 100% well. Perhaps you have a slight cold, stomach cramps, a headache or a hangover.
Last Sunday, I felt very under the weather. Unfortunately, it was completely self-inflicted! So, no sympathy required!
Why don’t I learn that it is never, ever, a good idea to mix lager and red wine?!
Anyway, personally speaking, the hangover is definitely the reason why aspirin was invented; and on a positive note, over the years I have kept a lot of chemists in business as a result of my aspirin requirements. OMG, I’m a total business angel!