I'm another with diagnosed poor supply and we had to mix feed from 13 days old. Just wanted you to know that using formula doesn't always meant that they'll go off the breast - we had success with the Calma bottle, but that was after weeks of syringe feeding and tube-on-boob (SNS) feeding. 10 months later, and he still loves his boob-milk, despite the fact that he has had both BM and Formula all his life.

I second the 'get a really, really good pump' advice. And a double pump, cos that cuts down the time it takes to pump, and you need to get all the rest/sleep you can.

Also, I found that my late afternoon supply went up significantly on days I had an afternoon sleep. I know this for absolute sure cos we had a borrowed baby scale, and was weighing pre-and post feed to know exactly how much BM he was getting, and was recording it on charts for a couple of months.

Good luck. I know just how stressful it is having a baby that doesn't gain weight.