Can an infant become lactose intolerant suddenly? My daughter is almost a month old and EBF. We've had no problems until last night when she fell asleep and suddenly woke up with a weird cry about 10 minutes later. I got her back to sleep and she was fine the rest of the night. But today she's been weird too. Still has a weird cry. Almost like a pain cry instead of the usual where she's just trying to get attention. Also she started spitting up today which she's never done. I have an appointment with her doctor Friday and I'll bring it up just wondering if anyone has any ideas?