Boobs suddenly deflated?

[roslily]

Since yesterday they haven't been 'filling up' as normal, they have completely shrunk. I can even wear my pre-pregnancy bras.

Is this normal? I have been BF for 4 weeks

in my experience my boobs filled and kept refilling until i started weaning.
are you feeding every 4 hours or so even at night?

I suspect our supply has adjusted to demand so you're not engorged any more, if your baby is still doing plenty of wees and orangey poos then the bf is working.

*your