How much formula for one month old?

My baby girl will be one month old on Wednesday. She has been a very calm baby up until this past week. It seems like every time I feed her, she is getting hungry immediately again. She is eating a full 3 ounces right now, and I’m afraid to do anymore because I don’t want to make her sick. She gets so fussy even when she doesn’t have a dirty diaper, no evidence of a tummyache, or any other issues going on. The only thing I can think of is she is still hungry, because as soon as I offer a pacifier she starts sucking aggressively but soon spits it out and starts screaming. But if I offer a bottle, she is eating it and gulping it down. She doesn’t even go two to three hours between feedings before getting hungry again. The only reason I haven’t bought her 4 ounces is because she spits up a little after eating 3, which makes me think she’s too full.. maybe I’m wrong but I am curious!!!