Yes, I have advice. I went through similar, long long ago.
Stop worrying. The milk will come.
We are blessed that we have good formula and hygiene, running water etc, so it isn’t a tragedy if we have to give formula.
For now, schedule your formula feeds. At all other times, keep the baby at the breast. Eat regularly but apart from that, stay in bed with your baby at your breast. Give free access, as much as your baby likes. No pacifiers.
Throw your pump away. Practise stroking your ‘spare’ breast, while the baby is at the other. This will be enough to express. You probably know this but start by making a circle with your finger and thumb. Put the place where finger an thumb join at the tip of the nipple. Gently slide your finger and thumb up you breast, about half way. Your circle will have opened but that’s ok. From halfway, with thumb on the top of the breast and finger underneath, slide finger and thumb back to the nipple, pressing very gently. The first time I did this I got one miserable drop, but within a few days I could do 2oz at the drop of a hat.
A lot of nonsense is talked about mixed feeding. It’s not the end of breastfeeding. I was able to slowly reduce formula as my milk supply increased, and within a few weeks dd was fully breastfed. She continued to feed until she was 4.3.
Please don’t worry. You can do it.