Newborn not gaining weight- Help please!

daisies916

Background: 

LO was 7 lbs 2 oz at birth and dropped to 6 lbs 2 oz at her lowest. She is currently hovering at 6 lbs 4 oz with little change no matter what we do. We had a rough start. She had a posterior frenulum, so we didn't have a successful latch until 2 1/2 days into it (after we got it clipped). We are using a shield and she is nursing like a champ now. 

We have done the weighing thing (before and after nursing) and she is transferring plenty of milk. She has plenty of wet diapers, but she doesn't have many poopy diapers. Our nurse/LC said that it was probably b/c breast milk is 100% usable and she was playing catch up b/c of the latch issues and using every bit of the milk. 

We tried to supplement with breast milk and a syringe and tube while she was nursing. She hardly took any of it and those were the only 2 times she spit up. I've tried to increase her nursing (I was letting her sleep too long 3-4 hours sometimes between nursing). 

I let her nurse completely on one side and she has access all the time. She's not in my arms maybe 1-2 hours total all day and night. She will not take a second side when nursing. She has fallen asleep  and just gets mad and won't nurse if I wake her immediately. I do wake her for her regular feedings, though (now every 2 hours). 

I've  tried everything our nurse/LC has suggested. I've poured through breastfeeding books and websites. I don't know what else to do. We've attributed part of her lack of gaining to genetics (I have a very high metabolism and don't gain weight easily or quickly). 

I'm  afraid they are going to want to do formula. I REALLY don't want to do that, but I'm starting to worry. FWIW- she doesn't act hungry after she eats and she isn't constipated. She's a very content baby who loves the boob! She comfort sucks a lot. DH is really starting to stress about her weight gain, too.

Has anyone had a slow gainer? What else can I do? We go for another weight check on Thursday but we bought a baby scale and weigh her daily. Help please!