Breastfed and formula combined HELP!!!

Are there any parents who do both? Giving formula and breastfeeding. My child is 1 month and 3 days and I’m just not producing enough to pump and feed. I have been trying to store milk up for when I go back to work on January 4th but as of right now I just have 3 days worth and I just feel it’s not enough. I’ve heard of some babies being given formula at daycare and then breastfed when with the mom. I want to continue to give milk when I can and I’ll continue to pump at work to have for him but I think we are going to have to start giving formula every so often. So if anyone has some advice it is welcomed. Thanks in advance!