Bf advice

Long story

My supply isn't increasing and my supply is too low for my 19 day old. She's always crying and the Dr was concerned for her weight loss. I broke down and bought a small can of newborn formula to fill her up longer after nursing. I can only pump 2-3 ounces every three to four hours so I've been pumping almost every 45 minutes to an hour to help stimulate that they need to produce more but it's not working so well, or at least not yet. (Day 2 of this).

I want to do everything I can to boost my supply faster. Any input is greatly appreciated!! Please and thank you