A.F.
Hi L.,
I had a really tough time nursing too and had to supplement. Don't feel bad! You did a great thing by nursing at all and don't let breastfeeding Nazis crab at you. Most of them never had trouble and they get all their info from a handbook, not from real people.
I would recommend doing breast milk and formula at the same time as it can be hard to digest the formula, it might make it easier to transition. Also, that way she will still benefit from the antibodies in your milk for the months that you have stored up.
Pumping is exhausting, emotionally and physically, and you have done a great job!
Blessings on you and congrats on the new baby girl!