How to know if you need to supplement with formula?

Tiffany • Our rainbow baby girl was born 3.30.2018 🌈👶🏼 Hoping to conceive baby #2 before the year is over 🤞🏻

I am a few days shy of a successful 10 months of breastfeeding 💪🏻 but I am constantly wondering is my baby eating enough? My mom always asks “how many ounces of milk does she drink a day?” (We were all formula fed) She always seems puzzled when I say I have no idea she nurses 4-5 times a day 🤷🏼‍♀️. My concern isn’t my moms questions. I just feel like right now my LO is teething and possibly going through a growth spurt so she is nursing a lot! And sometimes I feel like nothing is coming out after awhile and sometimes she’s still fussy after eating. Is it her teeth or is she not getting enough milk? Is it too soon to assume it’s a lack of supply? I do have one very lazy breast.