Why is she like this when she eats?

I have a 1 month old, and she's been bottle fed since 1 week. When we first started bottle feeding, we had no problem, she took the bottle great and was happy with it. Lately, and it's only been getting worse, she'll take the bottle happily, then after a few sips, get really upset, spit it out, cry, and repeat. It's become a challenge and a chore just to get her to eat. She'll be dry and burped and wide awake and she'll still do it. We didn't change formula either, it's been the same thing since we started her on it (Enfamil gentle ease), also same type of bottles and nipples. Literally nothings changed. Why is she doing this when she was doing so well in the beginning? What can I do? I wanna enjoy holding and feeding her again, not dread it.