Strict formula

My little one will be 4 weeks old Christmas Day. I was breastfeeding/pumping and supplementing with formula when I wasn’t pumping enough. I only had to feed my little one about 3 formula bottles a day now when I pump I only get less than an ounce. I’m looking to go to strict formula because I’ve tried everything I don’t what else to do. It’s just a little depressing to go straight to formula when I had my mind set on giving breast milk.