its possible...But remember you need to eat more food so you can pump more milk. Dont try to be going on a diet and make sure you drink PLENTY of water.
how much milk you produce depends on supply and demand. try to pump more often so you can trick your breast into producing more milk. In fact, try power pumping once a day to up your supply.
how it works for power pump is, once a day you pump 20 mins, followed by 10 mins rest followed by 10 min pumping followed by 10 mins rest and do the last 10 min pump again. It will total up to 1 hour. So its 20P-10R-10P-10R-10P. It mimick a baby"s cluster feed and will make ur breast milk produce more milk.
Dont feel guilty about giving formula, I also was in the position as you in the beginning. Just remember "Fed is best" so if ur baby is hungry, if there's BM give BM if not, give her formula or do a bit of both until you can slowly up your milk supply.
pump 15 mins every 3 hours. At night, normally I would just skip cos Im too tired, but otherwise, try to be consistent. Refrigerate those milk so you can quickly put in bottle warmer when your baby is hungry next.