Low Milk Supply

FT mom to a 3 week old, c section baby. I had to use a nipple shield in the hospital and bought more for home but he was losing too much weight so we supplemented with formula and I pumped. I haven’t gotten more than 5ml of milk at one time while pumping. I’m drinking plenty of water, but I just cannot get my supply up. My boobs do not feel full or anything. I’m so frustrated and upset with my body for not doing what seems to come so natural to others. I have severe food allergies so most lactation cookies and such are a no go for me - this is definitely ramping up my anxiety and depression and I’m trying to avoid PPD as much as I can but this is sooooo not helping.