Advice?

My daughter is 12 days old & is usually very good, very quiet, and very happy. She rarely cries, sleeps through the night (other than feedings), and has only spit up a few times. But all last night and today, she's acting constipated. She pushes until she's red and there will only be a spot of poop about as big as a nickel. She's been fussy and when she does get a little bit of poop out, it's still yellow in color but seems a little runnier than usual (she is breastfed). She's also been spitting up a lot today, every time she eats anything.

What can i do to help her? I feel bad that she doesn't feel good. Someone suggested gripe water but is she too young/little for that? She weighs almost 9 pounds now.