Baby lost weight

My 3.5mo LO had been gaining weight steadily since birth and just recently (for almost a month) she went from 6.2kg to 6.02kg. She's not fussing and has been fed on demand, typically every 2hrs so it's either she's not drinking enough (direct latch) or I'm not producing enough milk to satisfy her needs. Is this normal? FYI she has been rejecting FM and the bottle, so as per my MIL's advice, we've been trying to train her to accept the bottle. Worried that the stress has been causing her to lose weight.#advicepls #1stimemom #firstbaby #worryingmom #pleasehelp