Supplementing with formula

I’ve been breastfeeding since day 1 with my baby boy. He’ll be 6 weeks on Monday. We went into the doctor for an unrelated issue. Our doc states his weight gain is lower than expected but not of concern.

I’ve been considering supplementing lately because breast-feeding and entertaining a five-year-old has been a challenge. I’m not sure I’m making enough for my little one, I let down is very fast and we always end up with choking in massive spit ups when nursing. I’ve also noticed that he seems a bit smaller than other six week old babies.

My question to you is if you did start supplementing how did it go and how does supplementing and breast-feeding work for you thanks ladies!