Breastfeeding and baby weight gain

Lulu
Is anyone else not quite keeping pace with the ounce-per-day baby weight gain recommendation? I am breastfeeding on demand and all seems to be going really well, but I only helped baby put on about 2oz. last week (her first/second week). It makes me feel so sad/bad. :/ I really want to avoid formula supplementation if possible. Any help/support is appreciated