I remember the first day I left my daughter for the entire day. Beyond the discomfort at being away from her the whole time, I only had maybe 15 ounces of breastmilk stored in the freezer, plus what I had in the fridge. During the day, I pumped my heart out and thought I did really well- there was NO WAY that she had drank that much. I felt great, and was looking forward to getting home to see her.
When I got home I found, much to my chagrin, that she had drank EVERYTHING in the fridge and the freezer.
Now part of this comes from the fact that feeding a baby breastmilk and feeding a baby formula are slightly different beasts. Formula is, for the most part, an unlimited resource. Breastmilk, as we all know, is not. Thus there is a difference in how to feed them from the bottle with expressed breastmilk. Mainly, you want them to want the milk, you don't want to turn the bottle upside down and let gravity do the work (this is also helpful because you don't want the bottle feeding to be SO MUCH easier than breastfeeding). The concept of paced bottle feeding is what I found most helpful. You can find this on many sites, but the idea is this:
- Feed the baby in a more upright position (not lying down flat), don't just pour it down their throat.
- Use smaller increments and assess the baby's needs (a sign of overfeeding is spitting up a lot because their little digestive systems aren't fully developed) and use a slow flow nipple.
- Use hunger cues, not a schedule (if this is realistic for you),
- Switch sides (to help mom so baby doesn't decide they like feeding on one side only),
- Extend the feeding, let them take little breaks to mimic your letdown and don't force them to finish the bottle if they don't want to.
There are lots of places you can find this method described too.
It was an almost daily struggle to keep up with her, I wasn't lucky enough to be a "super producer" and (gasp!) I always had a container of formula ready to be used *just in case.* The most important thing is that your baby gets sustenance, it was both a motivator for me to keep pumping (because I really did want to exclusively breastfeed) and a safety net, I knew she'd always be safe and well fed even if I had a bad day.
Also remember, sometimes they'll have a huge increase in consumption, but this might be a growth spurt and you'll catch up the next day when they're sleeping a lot. And remember, breastfeeding a demand and supply situation, not a supply and demand; the more you pump and feed your baby, the more you'll make.
You'll be ok, I promise.