You shouldn't feel guilty whatever choice you make.
We stopped breastfeeding very quickly because it just wasn't working for us. I was in pain, I have flat nipples and like you I have very pale skin but I didn't realise that might contribute to our difficulties. Mine are also ridiculously sensitive. I don't think I was producing much milk and I felt at a loss to know what to do. I can remember getting up in the night and sitting with Joseph crying my eyes out over the pain and the isolation and exhaustion.
The very worst was that he fed better from one breast rather than the other, we were better at latching on one side. I know they say not to do it but I found that he would feed better and sleep a little bit longer if we used that side so I let him feed more from there. The other nipple was absolutely raw because we had struggled so much so at first it was a relief but short lived because that breast became swollen with milk and the other was constantly in use so that nipple soon caught up with the other in the painful mess.
Just the thought of him wanting feeding made me want to cry or hide.
The final straw was a combination of realising I was bleeding into his mouth and almost being hospitalised because of his weight dropping so much. The day we stopped he kept latching on and pulling away again and it was agony and I could feel milk running down my skin but when I looked down I realised the liquid was blood not milk.
I don't want to tell you what to do, all I can do is tell you about our experience. I chose to stop breastfeeding and use formula, I felt instantly better for making the decision but incredibly guilty because I had wanted to breastfeed.
I was able to get more sleep and my breasts felt better after a few days, my nipples healed, I stopped feeling so alone and isolated in my own house because I was able to go out (while we were breastfeeding I needed to be positioned in the right chair with no end of cushions to support us, my feet on a stool, Joseph on a cushion etc) and because my husband could help with the feeding I felt more rested and he bonded with Joseph much better.
And most important of all, Joseph became happier, more satisfied and started to gain his weight back again so he was healthier too.
I struggled a bit because the only group running in my area at the time was a breastfeeding cafe so socially it restricted me from meeting other mums and babies and I felt very guilty. I felt that I had let down not only Joseph but the two midwives who had done their best to encourage me while they were here. If they could have moved in with me for a few days we might have continued.
But really, I didn't need to feel guilty and nobody else does either. Nobody has the right to make you feel guilty for making a choice to feed your baby in the way that suits you both the best but I think most of the pressure comes from ourselves rather than anyone else.
You need to be happy in order to make your baby happy. I'm sure that my crying with pain contributed to Joseph's struggles and weight loss and I would have felt guilty about that if we had gone back in to hospital because of his weight loss.
It's good that you are posting for support but only you can make the decision and nobody should judge you once you have, not even yourself. If you want to change to expressing or a combination of breastmilk and formula or just formula you don't need permission because you've done amazingly well to even try breastfeeding. And if you decide to continue to breastfeed I'm sure you will have a lot of support. But it's you and your baby that are important here and both of you need to be happy but nobody else matters.