So, my baby is having a hard time with her formula.

I breast feed and use formula but I think the formula hurts her she is using the Gerber gentle formula right now but everytime I feed her she is extremely fussy and cries during her feeding she does it with my breast milk as well idk if anyone has encountered this. But I would love some type of advice it hurts me to see her suffering so much. I even have tried 5 different types of bottles and nipples idk what it could be. I go to the doctor tomorrow but it's so hard on me to see her struggle to eat.