You do what you need to do, so that the baby gets enough intake, daily.
Some will say never supplement.
Some do.
It is up to you.
I breastfed both my kids and had lots of milk production.
But when pumping, I did not get much, though I tried different pumps.
Then, my daughter would not take a bottle at all.
My son would.
Just beware, that some babies will NOT take a bottle.
Or, some will but then may only want a bottle and then refuse to nurse from breast. Because, nursing is more difficult, than just drinking from a bottle via gravity. They don't have to "work" at getting the milk out.
The thing is, you do not have enough stored milk.
And at each growth-spurt, a baby naturally needs more intake and they get hungrier, more frequently and want more.
3 months old was a growth-spurt, and then there will other growth-spurt periods at 6 months, 9 months, 12 months and every 3 months.
So, in order for baby to get more intake and adequate intake everyday, you need to make sure, he is getting enough intake.
And if you don't have enough stored breastmilk, he will not be getting, enough intake. And babies need to feed, on-demand.
Or ask a Lactation Consultant, per pumping.
For me, with my son, though I had enough milk production, he'd drink me dry... (I used both breasts) and he'd want MORE. Per our Pediatrician, I supplemented. But only AFTER... a nursing session. If/when needed. (never to replace a nursing). My son had a GINORMOUS appetite and nursed every 2 hours and every hour when going through "cluster feeding." I nursed on-demand.
However, at about 1 year old, my son started to HATE nursing and only wanted a bottle. Then he weaned, from breast.
The bottom line is: a baby needs to get adequate intake daily. And if not, this is not good. Or, some babies will not nurse at all, until Mommy comes home. But, then the baby is hungry ALL day and they are not getting intake during the day. And you do not want a baby to get dehydrated as well.
So do what you need to do.