Help!

My baby will be 4 weeks old on thursday. I gave up pretty quickly with my two older children (8&3). We don’t have any latch problems. Only problem is my supply. I’ve had to supplement with formula for her losing too much weight. I have tried eating oatmeal, store bought and homemade lactation cookies and shakes, plenty of water, milkflow and milkflowMAX supplements, pumping or latching her every 2-3 hours AND I’m only getting an ounce of breast milk total. Am I not cut out to breastfeed my baby?