Can my supply still increase after 12 weeks?

Ni

We struggled in the beginning with breastfeeding so I began exclusively pumping. Was doing well with it but my supply was just enough for him- I built a very small stash, nothing to write home about. I usually pumped 2 ounces each breast, sometimes less...for a total of usually 3-4 ounces combined each session. Well we decided to go back to exclusively breastfeeding so we did. My little guy was gaining weight great! Even getting a little chunky. Well the other day I noticed he looked thinner...wasn’t sure if it was because he’s growing longer or not gaining enough. So I started weighing him on his baby scale and he kind of stayed 12 lbs. 10 oz. for a few days 😓 it got me worrying!!! I weighed him the other day and he’s now 12 lb. 13 oz. but that’s like in a whole week! Thank God he at least didn’t lose but is this normal? He just turned 3 months this past 28th. He never seemed hungry or starving! He eats and pulls off himself. He doesnt nurse for too long- maybe 4 minutes one breast and 2 the other- our average has been 6 minutes each session from the app. I’ve been trying to encourage him to nurse more but he pulls off...is it because milk stopped coming out?

So my questions: is this normal? Is it possibly my supply? I’m wondering if I should start pumping and bottle feeding him again so I can see what he’s getting?

Any advice helps please 😭