She's only 3 weeks on Wednesday. My MW said today it's unlikely it's an issue with dairy because she's too young for that. I don't know, I'm doubtful about that advice... anyone have experience with a very young baby?
I also remembered something else I ate that could have caused the horrible diarrhea episode. My husband made a quiche with eggs and spinach in it. That was the first time I'd had either eggs or spinach since she was born. The MW mentioned it could have been the spinach, since that's a gassy vegetable. In any case I'm now basically monitoring everything I eat and going to try and not overdo the foods but take in smaller portions each time I eat something new or that might possibly cause a reaction, then try and note any changes with Emma's gas and poos. I just hope not to have a repeat of Saturday, that was really scary for me. We ended up giving her some formula overnight while I waited to pump again/start over because I didn't want anything I'd already pumped to cause more trouble. For the record, she's been perfectly fine since Sunday morning's pump feedings + with the formula.
Finally, I also talked to my parents who noted that when I was a baby my mom had to stop breast feeding because I had constant projectile vomiting and diarrhea, which were causing (obviously) constant colicky behavior and much distress for everyone. They switched me entirely onto formula after a month. My brother was also switched to formula soon for some of the same reasons. We have our first post-hospital pediatrician visit this Friday (the one month visit) and I am going to bring up this issue at that point. I am willing to breastfeed as long as the baby is happy, but I am not willing to do so if she has issues, and I am perfectly fine switching entirely over to formula if that's what it takes to make her happy and content (happy baby = happy mommy and daddy). Besides, after talking to another woman today about both her lactose intolerant children, both of whom turned out fine and with whom she switched over to formula after several months and then one month (she got them tested for cow's milk allergy too), I feel much better about formula than I did before. She told me that sleepless nights of agony and pain for her kids pretty much disappeared after she started them on lactose-free formula.