She's not getting enough, and I feel so sad.

Elowyn was born a week ago and weight 7 lbs 9 oz. As of yesterday she's weighing just 6 lbs 5 oz. From the second day she was born I was having excruciating nipple pain. When I was in the hospital I saw 3 lactation consultants who all told me she was latching perfectly. But the pain has continued. I haven't been able to breastfeed without taking heavy painkillers that they prescribed me. My nipples are so beat up. She hasn't pooped since we left the hospital a solid week ago. She barely had wet diapers and they were super yellow. I knew she was really dehydrated. When I nursed I would go as long as she wanted and she never fussed for more milk. She is super jaundiced at this point and sleeps SO much. So I went to the l.consultant yesterday. She told me that the pain in my nipples is caused by Elowyn bruising me. And because the pain is so intense my milk has slowed down significantly. So she's not getting enough milk at all. When I pump I only pump about half an oz to 1 oz per session. The consultant told me that it should be 2 oz per session. The pediatrician came in and they both told me that the plan is to just pump and give that to her in a bottle until I go back on Friday. They also want me to supplement with formula. Elowyn's daddy is SO against formula but I feel like at this point she's not doing well and she needs just a little bit of it until I'm producing enough. So I've been sneaky giving her formula during the night while he's asleep. I feel so so sad that I'm not providing enough for my baby. I cried all day yesterday and I worry that I won't be able to produce enough milk. Women in my family have a history of being horrible breastfeeders. I guess I just needed to vent a little bit as my SO doesn't really understand my feelings and I live far away from family and close friends. If anyone has any advice or thoughts on this I'd absolutely love your opinions. TL;DR: Breastfeeding not going well, she's not gaining, I'm really really sad about it.