Constipated six-month old. What would you do?

My son picked his baby up from her bio-mom Thursday night. She hasn’t had a bowel movement since then. The thing that has me concerned is that every 15 minutes or so she tries to poop, she’s straining, but very little comes out and she starts crying,as if it hurts. I remember my son going a week without pooping so that in itself isn’t so alarming, but he didn’t cry when he tried. That’s what has me concerned.

He’s been giving her Karo sugar bottles along with her formula. That always worked for me.

Would you take her to the ER? I think I would.