3 months and not content after eating

So my baby has been having a lot of trouble after she eating. She cries and screams (like she wants more) sometimes she will burp good and sometimes she won’t. But it doesn’t matter how much I give her, if she burps good or doesn’t she’s never content after eating. Has anyone went from feeding their baby 5-6 ounces every 3 hours or so to 4 ounces every 2- 2 1/2 hours? I’m thinking about trying this because maybe 5-6 is just to much for her at one time...I’m wondering how this will go though since she’s been on 5-6 for a while now. I did call the doctor when we moved her to 6 and she started to get fussy she said maybe try 5 ounces, we I did and it helped a little but she still cries and screams after she eats. She’s 3 months old...why don’t we have her feeding down yet?!?! It’s driving me crazy! I did feed her more this last feeding just to see if it helped and it was ten times worst, she seemed uncomfortable, cried off and on, was grunting, spit up a lot etc....she did this for a hour and a half. I’m just so lost, idk what to do.