Insufficient Glandular Tissue and breastfeeding

I’m currently two weeks postpartum and I am struggling with low milk supply. I had low milk supply with my first child and this is now my second. I have transitioned over to my normal breastmilk, but I never felt my milk come in or engorged. Currently I am supplementing with formula. I breast-feed about every three hours and then supplement with 2 ounces of formula while pumping an extra 10 to 15 minutes each feed. I think my baby is getting less than a half oz each feed and I also pump less than a half oz. It took me a whole day to collect 2 oz of milk. My lactation consultant thinks I have IGT. Does anyone have recommendations on how I can increase my milk supply so I don’t have to supplement with so much formula?