Hi, I am by no means an expert in this , but couldn't read and run as I was in a similar position with my now 8m DD.
We really struggled with BF and she lost a lot of weight, over 10%, I was so so stressed. Plus BF was agony as she struggled to latch due to flat nipples (they are no longer flat). We did do top ups for 2 days with formula, plus pumping, but then I stopped as I didn't want to anymore, so focused on pumping and BF LOADS!
So, firstly, I fully agree that fed is best. If you want to move to formula there is absolutely nothing wrong about that!!!!!
However if you are wanting to continue BF....have your health visitor team or infant feeding team (think midwifes can make this referral but maybe HVs can too) come in to support with weighed feeds etc to see how much breast milk she's taking? Does she feed well and how long for? Does she seem satisfied after the boob? Like drowsy or content.
Pumping will help increase supply but so will offering lots of feeds. I know it is tiring, and it takes up your day. If it's starting to consume or upset you then you need to do what's best for both DD and you! You are important too.
How many feeds a day does she do? In the early weeks I was offering like 12 -14 feeds a day throughout 24 hrs as DD would only feed 5 mins at a time!
Make sure you're drinking tons of water, and plenty of nourishing food. Is your partner supporting ? If you can't seem to find time to cook and eat, simple things like overnight oats (oats are apparently good for supply), lots of wholemeal toast to fill you, fruit, quick but reasonably healthy things if you see what I mean.
Sorry for all of the questions, trying to get a full picture. And sending hugs as I remember how exhausting it is 💐 remember, you're doing amazing. Be kind to yourself.