Baby throwing up milk.. HELP‼️

My baby boy Kamden is throwing up all his milk & he has thrown up formula as well. He been doing this since birth but it’s gotten a lot worse lately. His dr told me to give him more milk & even if he’s throwing it up.. she said he will still probably gain weight. Idk how he could though he’s vomiting so much. She told me I could try rice cereal or Zantac.. I’ve heard negative things about Zantac so I’ve been trying to stay away from it. He’s 6 weeks old Tuesday.. the weight chart the dr showed me he was at the bottom 😭😭 Any recommendations? Worried momma here..😭

He looks miserable 😭