FED is best. Don't feel guilty at all!I had to supplement with formula the first month too while my supply built up. I would only power pump once a day. You don't want to cause any damage to yourself, and it's so time consuming. Give it about a week to see progress. You're doing great mama!

Breast feed as much as possible, switch baby from one breast to another as much as baby will allow, them pump after nursing. And power pump in the morning and at night. Honestly at three weeks I wouldn’t be too concerned and I’m not sure why u would be giving formula at this age as their stomachs are soSmall they only need 0.5-2 Oz max. Also pump output isn’t a indicator of how much milk u produce. I’d highly recommend stopping the formula and bottles and just nursing as that’ll be the best way for your supply. Baby will take what u give them, so if ur giving Oz of formula in a bottle they’ll drink it even if they are full. It takes 30 minutes for babies belly to fill from the milk, so they could act hungry even though they are full. Please talk to a lactation consultant. Sounds like u are making more than enough milk for baby