1 week old constipated?

Jestice

My baby is 1 week 1day today & has been drinking breast milk and formula. He switched from Enfamil infant pro to Enfamil Gentlease & the gentlease caused him to have projectile vomiting & he’s now experiencing constipation. I’m a first time mom and have no idea what to do! He has his initial doctor appointment set for this Thursday coming up. What can I do in the mean time to get things moving again & get him feeling better?