I Need A Second Opinion. My Little One Is 3

I need a second opinion. My little one is 3 weeks and 2 days old. She recently has vomited twice in the past 3 days, had 2 green bowel movements, and has seemed to have a problem with bowel movements since a few days after coming home from the hospital. I've asked multiple times about whether or not she could be constipated or there could be something else going on. I'm starting to feel like she shouldn't have so many problems having bowel movements and passing gas.