Newborn constipation and diarrhea?

My baby was just born early last sunday morning. I started out breast feeding him but he wasn’t latching on well and I was in some pain so I switched to bottle feeding when he was 3 days old. We use Similac with iron. He had normal poops up til yesterday when he was constipated. Today he has had diarrhea. He isn’t running a fever and we didn’t switch formulas, we have always used similac if he wasn’t being breast fed. The pediatric office isn’t open until Monday, is there anything I can do at home to treat him?