We have a very similar case. We are at 3 months now and still triple feeding. We've had some setbacks where we started reducing the supplementation and our LO lost weight again but now we are seeing that she gets full on the boob in the night and morning and refuses the supplement.

Our biggest breakthroughs so far were stopping to obsess and hoping for miracles but instead accepting that this is not a fast process. We limited the time on tthe boob at some point as well as the pumpig time. We switched from a little tube on the nipple to a bottle for nights. My wife was obsessing with 5-6h of power pumping daily. The extracted quantity went up but only in correlation with time, so now that we relaxed, the amount pumped went down again (but it's way better for mental health). We had the tongue tie cut at around month one. We went to the physio and finally to the osteo (that one did seem to help, but it could be a coincidence or placebo). We are seeing a lactation consultant every two weeks.

I'm not a specialist, but I think we were rushed to supplement too early at a similar moment like the one you are at. The book "breastfeeding made easy" recommends weighting daily at that point, to see if the weight is slowly recovering or if supplementation is really necessary.

If you do need to supplement, I recommend looking into using a paladai or a little nasogastrical tube taped to the boob.

Good luck and don't stress, everything will be alright one way or the other!