Fed is best, but I'm still sad..

I am not entirely sure what to do at this point.

I have a lovely daughter who is now a week old. I want to breastfeed, but there has been several bumps on the way. She has been loosing weight and she's very sleepy. I've tried all the tricks to wake her up during feedings, but it hasn't worked. Feeding on demand hasn't worked either. She's been checked for tongue tie, but so far they're saying no issues there.

I'm not sure what to do or what to try at this point anymore.

I was asked to supplement with formula because she just didn't gain weight. We've done that, but I'm afraid it'll end our breastfeeding journey prematurely.

And having her fed is by far the most important, but I know I have milk so it's still a bit sad. I had hoped it would work out 😔

Edit: I've been pumping. I can't keep up unfortunately. I don't pump enough out. She eats it faster than I can get it out.

Another edit: Loosing weight is normal, but she lost too much. She continued after my milk came in. That's not considered normal here.