Hi Mumof2Boys, wow it is amazing what you're doing. And I think it's great that you're expressing your anger. I too have felt a lot of anger at various things, like breastfeeding not going to plan (basically I'm on the verge of weaning too) four years of IVF/infertility to have a baby and an unplanned caesarian. Your daughter will love you and need you, no matter what.
I think switching to formula would be a completely sound decision for you. I know that doesn't help with your grief and anger, but please don't beat yourself up about this. Your baby's sucking is totally out of your control. You have done nothing wrong. And if you want to persist, if that feels right, then see how it goes.
I just hope that you take it easy on yourself and get a tiny bit of peace soon.
Best of luck,
WW