Baby's weight!

Hi! My baby is 3 months old and she slowed down a lot in the weight gain! She's eating 7-8 times a day until she wants to stop and she's a happy baby, not fussy or cranky! I went back to work and she's been feeding from the bottle which I know she doesn't love but still eating between 3-5oz per feeding. Also, she slowed down a lot in the poopy diapers. Sometimes she goes 1 day or two without one. Should I be concerned?? I don't have a doctors appointment until next month but I'm not sure If I need one sooner. I don't want to be paranoid but it really concerns me that she could be undernourished. Did someone have a similar situation with their babies? Thanks!!