Often it is food related.
If you are nursing, then pay attention to what you are eating just a bit. Some babies just can't handle certain things for those first 3 months.
I know my last baby HATED coffee and chocolate...which I was drinking a mocha every morning (I'm usually a health food nut, but I was on a binge--hey, it was my 4th baby in 5 years--I figured I was entitled to a binge!

)...
So he spent his first 3 weeks screaming his head off every evening... As soon as I figured it might be coffee...and then figured the chocolate wasn't so good either...he was a little sweetheart!
One baby was a 2 week old when I went to a family picnic...and ate chips with jalapeno cheese dip... Let's just say she didn't approve! Poor thing screamed for about 4 hours straight once those jalapeno's hit her system, about 5 hours after the picnic! It was TERRIBLE. My husband commanded me to abstain from the dip for the next 3 months, let me tell ya! *grin*
Usually what you eat will get into the breastmilk about 4-6 hours later. So keeping a little log of your foods will help you figure out what the offending item or items may be... Many babies can't take gassy foods (like brocolli or cabbage), whilst others can't deal with anything spicy...others it's acidy foods like coffee, about 1/3 of babies can't deal with chocolate (a shame, I know!), while others have a problem with dairy (my best friend can't drink milk when she's nursing a baby)...etc... A food log will really help narrow it down for ya!
And, keep in mind, their digestive difficulties go away after those first 3 months (usually)...and then you can go back to your same old foods!
It's a pain to go off your favorite foods, I know, but nursing is so awesome that it's worth it!
Blessings,
Molly
Your CF lactation consultant (harharhar)...
Moooooo....