Hello, our 3-week-old baby is vomiting forcefully after feeding; it ev…

Hello, our 3-week-old baby is vomiting forcefully after feeding; it even comes out of the nose. He vomits constantly. Because of the quarantine we can't reach a doctor. He also has jaundice and hasn't pooped for a day; he's suffering and straining. What should we do, how can we help the baby? We hold him upright for 30 minutes after feeding but it still doesn't help.