Constipated one month old

my daughter was on similac advantage until she became colicky. I switched her formula last Tuesday from similac to gerber smoothe. She was pooping great until Monday. I noticed she pooped a pebble, and after she pooped normal. Never thought anything about it. This morning was my scare.. this was 9:30am

She pooped again at 10:15am

And that's what we got. Her texture and color are changing dramatically. I made her a doctors appt for 2pm today. I'm thinking it's from switching the milk and maybe I should give it more time to get use to her system. But she's been crying for the past 2 longgg days! Any suggestions? Or has anybody experience this? I never had a problem like this with my first baby and he was on sensitive similac for lactose.