Feeling guilty and unsure whether to continue

I have a 3 month old, and initially I resented breastfeeding a lot. Bubs latched perfectly, and fed really well but I had an oversupply and she cluster fed constantly for the first 6 ish weeks and I found that really challenging. To help with the cluster feeding and to feel some freedom I started giving bubs 1-2 bottles of formula in the evenings. I did try to pump first, but it was causing my breasts to become engorged constantly and was so painful.

Over Xmas, my partners family came to stay with us for a month (they live on the other side of the world). It was like there was this expectation that they would have baby all the time because they wouldn’t get to see her again for a long time. On one hand I was greatful and I got some extra sleep in the mornings, my partner and I got to go out together etc. but his mum had these strong opinions that I should stop breastfeeding since formula is fine (as that’s what she did for her kids). They didn’t seem to respect that I wanted to breastfeed, and they kept giving her bottles without checking with me first. I would go to feed her and then be told “oh I just gave her a bottle while you were in the shower” etc. they would say she was desperate for one and couldn’t wait or use helping as an excuse (e.g., I thought you could use a break so we’ve just given her a bottle), pretty much any time I turned my back lol. I was still breastfeeding over night and maybe getting 2 feeds in a day.

I did try to pump during this time once I noticed my breasts stopped leaking etc, but it was destroying me mentally, I felt like I was just locked in a room over Xmas pumping so everyone could feed and spend time with my baby.

Once they left, I really wanted to get back to breast feeding her fully and to strengthen our bond as well. Unfortunately my supply has absolutely tanked. I can still feed her over night but during the day she will start with a breast feeding, get really upset on my breast (pull my nipples, frustrated noises, thrashing her legs and arms around), then will drink a 100ml bottle of formula afterward.

I don’t know what to do, I feel so guilty for letting the feeding go, I have tried for over a week now to breastfeed her for every feed, and she always requires a top up and gets upset. I don’t know how to get back to where we were and I’m stressing because I’ve really grown to love it after such mixed feelings initially. But I don’t want to cause her more stress, I don’t want her to struggle when feeding. But I don’t want to give up yet.