Hi Manuka, I'm sorry that you feel bad at the moment. Whilst there are many positives to B/F it is not the only thing that denotes your success as a mother.
I used to prattle on in my pregnancy at how disgusted I was with mums who used disposable nappies and that I was certainly not going to contribute to land-fill and expose my babies bums to nappy chemicals etc....you get the idea.. however after my long first labour and birth I was shattered and all my good nappy intentions were thrown out the window.
I reached a point where I realised that motherhood doesn't always go as you'd planned or anticipated and hoped. I've learned with my DH to develop the confidence to do what is best for us as a family at the time, with the information we know.
It sounds like you had a traumatic labour and birth which still upsets you. It sounds like you really tried to express and B/F but it didn't work out and at the time if you were that ill then introducing formula was probably your last option.
Try and look at all the other wonderful things only you can provide for your child, like giving your time and love. Are you making her own solids food (if shes weaning?).
I'm sorry I'm not sure I'm really helping very much but I just wanted to try and make you feel better. It may help to try and talk to your family and friends they may understand more than you realise. I read in a survey somehwere that not B/F is one of the biggest things mums feel guilty about in later life and as much as I promote and go on about B/F it is not the only thing that makes motherhood and your child healthy, loved and successful. With everything that has been thrown at you, don't feel bad, you have a beautiful healthy girl who you just need to enjoy.