Is this normal?

My daughter will be 4 weeks this Tuesday and I have been exclusively breast feeding. She lost 11.9% of her birth weight and when she was weighed it was discovered she has a mild posterior tongue tie. I’ve been to two lactation consultants and our feeding has been viewed by them and a health visitor and a midwife who all say she latches beautifully and swallows big and so on. However, nearly 4 weeks and she has not regained birth weight yet and she constantly feeds! My question is, is it normal for a baby to pretty much be on the breast from 7pm to 11pm? Any time I take her off during these times she screams the house down like she’s starving and if she rolls off she wakes pretty quickly and screams. Recently for example she fed for 2 hours (an hour on each breast) would not settle and took 3oz of pumped breast milk. I’ve been told her tongue tie is not serious enough to effect feeding so why is she feeding for so long??? All the people I have seen and nobody can tell me. I’ve tried different techniques and she has a good latch. It’s driving me mad if I’m honest and making me want to give up breastfeeding completely! 😥😥😥