I had a breast reduction a few years ago and while my plastic surgeon said I will most likely be able to breast feed, I won't know for sure until baby is here and I'm predicting I will likely have to supplement.

This may be a silly question - but how exactly do you do both? Do you pump and mix breast milk with formula? Or do you do two separate feedings - one on the boob and then one with a bottle? How do you know the baby is getting enough of each or how much you need to supplement?