Constipation?

Nicole

I've looked online and looked through this app, and I can't find a straight answer. I had to give my 5 month old formula 4 days ago. Just 6 oz. Hes strictly on beeastmilk otherwise. He hasn't pooped since. He doesn't seem likes he's trying to poop ans doesn't seem more uncomfortable than usual. How long can he go without pooping before it's cause for concern.