I expressed from day 3 because of the pain. We are now starting to breastfeed again because I am finding it very restrictive having to express every 4 hours. The breastfeeding is not perfect but we only started yesterday and it's way better than it was at day 3!
I have a fantastic supply - everything she needs and then some (which either gets thrown out throughout the day as the end of feeds - the last 20ml in the bottle - or from time to time we freeze it).
We've never had nipple confusion. We use 3 types of bottles (Avent, Tommee Tippee and Breastflow), 2 types of dummy, she sucks on her hand, our fingers, anything really
She's had no confusion going back to the nipple.
Maybe express every other meal to give your nipples a rest but reassure you that she can still latch on. If I were you I'd express for a few days until my nipples had healed but I'm not up for extra pain if there's a way round it. Even now when I know it won't hurt if I put her on properly I am a it scared of breastfeeding and I don't really want to do it. In your situation I would start to dread every feed and that would make each day horrible and depressing. The number one thing for your baby in my opinion is a happy mummy.
If you do decide to express you may need to top up with formula for the first day or so - we did because my supply wasn't enough for her because we hadn't been feeding properly, it's possible if you are feeding properly that won't happen. A bit of formula won't do any harm whatsoever - she'll still be getting all the goodness from your breastmilk and just some more on top of that. And anyway, my brother was exclusively formula fed and he is a sporty fit doctor. Formula is not evil, especially if giving it once in a while (as you express to keep your supply up) means in the long run you breast feed longer because you aren't traumatised by the thought of putting your baby to the breast then there's no problem. I remember being a bit upset because OH had given Gabrielle a bottle of formula in the night instead of waking me to express and telling the midwife about this. She said it was far better for me to have got that sleep that I needed! After a little bit of expressing you get nicely ahead with the bottles in the fridge so you don't need to worry about having a crying hungry baby and no milk. We still have ready made formula in the cupboard just in case, but I have over a pint frozen and about the same in the fridge
I think at the age your LO is, Gabrielle was on about 75ml a feed of breastmilk, but that might not be right. We always just gave her as much as she wanted. Now she has about 130ml a feed, sometimes 160ml if she's really hungry or thirsty and she's been having that much since around 4 weeks. Each baby is different though and will ned and want different amounts.
Sorry that I've gone on so much! I hope it helps.
Good luck!