Baby not gaining enough, help

Hilary
Today was our weigh in, my dd is 17d and in last 2w only gained 5oz. Doc said she should've gained a minimum of 14oz. She is exclusively bf, and feeds around the clock. With no more than 2hrs between feeding but that's only once a day, otherwise she eats every hr. Doc wants me to pump and give her an extra 8oz minimum daily, or give formula. :( 
We need to see lactation consultant next wk and have another weigh. If it doesn't improve, her minor tongue tie and firm lip tie need to be snipped or switch to formula. I'm so sad and was in tears after our appt. I do t want to give her formula, and am scared about having her lip and tongue snipped. She latches ok and eats all the time. She just doesn't empty me even tho she feeds for 40-50min watch time. Any tips? Ideas? Could it be my diet?? My age? (I'm 41). I'm willing to do anything to prevent formula and snipping.