So ... i started a panic stricken thread over on 'chat' about this last week. Lovely posters suggested posting here.
DD is 3 months old. (15 weeks) In a nut shell she has failed to gain weight being exclusively breast fed, stuck at 8lbs :( However she is hitting her mile stones, growing in length, and showing no signs of dehydration or illness. She looks slim, but not 'thin'. Last Thursday, on the advice of HV and GP i began formula top ups to get her weight up. I'm not precious about BF, although i am sad to have failed.
I am keeping very careful notes of what she is taking and how often. At first i was going to do mixed feeding - but DD has taken to bottle feeding with a passion and is more or less refusing the breast since Sat., apart from a snugly early morning and late night feed.
She is taking 2, 3 or 4 oz bottles roughly ever 2 hours. (she sleeps through the night and has done since 6 weeks). The amount she is taking from the bottle is going up a little each day as she BF less. Today she has taken 28oz 
My question is really - is this ok? It seems loads! Dr Google tells me 32oz is the max recommended per day for a FF fed baby. Also - she is getting weighed again this Wed. How much weight gain can i expect? I am terrified they'll be none.
I think i just need a hand hold really. I've been so worried about DD.