Oh, EEEEP!!! I'm very glad it wasn't a heart attack, anyway. But, as other people have said, it may have been exacerbated by low blood sugar, which is surprisingly easy to achieve when you're feeling ill anyway and have little appetite. (As I know from personal experience.) Also, if you haven't had enough to drink, that can make one feel wobbly.

*puts on Official Aunty Marion Accept No Substitutes hat and glares sternly at Sam*

Keep warm, eat, slump in front of TV; and it's great that R is going to keep an eye on you!