This a million times over, OP.
I tried to breastfeed my DD, who is now 2. It was ok at first but then started to get really painful over the first day or two. She was feeding a lot and my nipples were so sore and bleeding that they kept scabbing over. Then every time she attached, she took the scab off and they bled some more. About five days after she was born, she fed for 1 1/2 hours straight. She kept crying and pummelling her little fists on my boobs - I am 100% convinced I wasn't producing enough milk for her. I had horrendous PND and couldn't eat any food (I literally couldn't swallow, it was like I had a lump in my throat). I'm guessing that didn't help with my milk supply.
I'm pregnant again and have just received the NHS literature for my hospital. In it are gems like 'your body knows how much milk to produce' and 'your midwife will confirm that baby is attached properly so feeding won't hurt'. Two separate midwives at the hospital and my own community midwife repeatedly checked and confirmed my DD was attached properly. But it still hurt. My hungry little girl was definitely not getting enough milk either. I don't give a monkey's what the 'experts' say - I knew by how she behaved that was the case. It's an instinct.
I supplemented with formula and my DD fed and fed and fed. Then, literally after the first bottle, refused the boob. I persevered but she was having none of it. So that was that. My midwife was actually fantastic - she said 'well, we believe happy mummy = happy baby". Quite. More of this please!
There are two whole pages of the benefits of breast feeding, how you shouldn't give your baby anything else, how you just have to get attachment right and everything will fall into place, how your body and your baby know exactly what to do. No mention of possible issues and certainly no reference to bottle feeding or co-feeding. It makes me so angry! This is exactly why when it all went wrong for me I sobbed and sobbed for days about what a failure I was and how I had let my daughter down.
And you know what? The worst thing is that I feel I constantly have to justify why I had to switch to formula. Why should I? I should be able to say "My daughter was formula fed". End of. Nothing to go with anyone else.
Sorry this is so long and ranty. It just makes me SO MAD.