Lots of tips of oversupply/fast letdown here -
Oversupply and Overactive (Forceful) Let-DownMight be worth experimenting with some of those to see what happens. But reflux can sometime manifest a little later, but, I think, usually before 3m (my DS's started around 6w).
If you've got concerns about reflux and have tried out some of the oversupply/fast flow tips, it might be worth posting in
Colic, Reflux, & CryingIf you're smaller, it could be that LO has been having some rapid growth in the early days (especially if there's been an oversupply) and is now going to start settling on a smaller weight gain for a while. My DD put on quite a lot of weight in the very early days and then it slowed down quite a lot, but she eventually found her own curve, albeit a lower one than she started on, but was still gaining weight. Probably good to keep an eye on it and check it's still going up, as well as wet/dirty nappies.