may need to supplement with formula

This is day four or five so far where it seems like DD either just don't want to sleep or is extremely hungry and can't fall asleep eating at my boob anymore. Usually she would eat while we're both laying down and she would fall back to sleep and stay asleep but for the past few days, it seems like it's just not enough anymore. I don't know if I should start bottle feeding her at night to help her go to sleep? She's almost three months old and she just spent ten minutes crying non stop before I gave her a bottle of thawed breast milk. Also, I'm wondering if I'm making enough to provide for her. The doctor showed slight concern for her weight gain at the two month appt - she's gaining but they feel as though she's straying off of a good path when it comes to the weight gain. I'm considering supplementing with formula - does anyone have any good suggestions on how I can start with that? Good brands? I'll still give breast milk when I can but if her hunger is increasing and I'm not making enough to keep her happy, I gotta do what I gotta do.