I can give you a selection of ways:
"not great but not horrible" ~ the body is very sneaky, and even a few extra calories at each meal for 5 days can certainly add up to a stall or an increase.
whatever the 'not great' food is, is it salty? very carby? that can hold onto water like mad, and water is heavy.
is it also TOM? that adds the water weight on.
Unless you overate by 18900 calories, this is not fat weight, 'just' water weight, which will whoosh away. honestly.
if you're not eating well, are you getting enough fibre? you could be seriously bunged up. (sorry about the detail....)
I suspect you're full of gunk and water, not extra fat. You'd know if you'd eaten 18900. this means that although it's really annoying, and bound to bring your mood down even more, it Will pass very quickly.
in the mean time, have a
, I hope you feel better soon.