Geesh. I was feeding DD this morning at 7 am (she was up for the day, I myself had only gotten 4 hours of sleep) and I noticed it was really thick at the bottom and had a hard time coming through the nipple while she was eating. I didn't know what was wrong so I took a closer look at it.
DUH I forgot to shake the bottle. Um, hello, how stupid am I?
And I made sure to not tell DH and to shake every single bottle today.