Ebf to EP

I was feeding on demand my 3 month old since she was born. I was never happy with feeding bc I never knew if she was full bc she would scream and cry 24/7. she had good diaper outputs well wet ones but poops would be small. since going back to work she’s been having bottles which have been way more easier and she’s more content. so I started pumping every 2hrs but i’m only getting 2-3oz when I pump that often. it I pump in about 4-5 hours I get around 4-6 and it I get really full from not feeding until the morning I get 8oz.. but I know it’s not good to have different pumping times. any advice? I don’t want to put her on formula i’m trying to keep up the breastfeeding but if I start supplying to low I’m gonna have to give her formula. good thing she eats 4oz right now. I pump just enough for her.. idk how this is even gonna work when she starts drinking more than 4oz i’m stressing out!