Reflux or CMPA?

Hi, my little one is 4 weeks old. She has suffered with what we thought was colic and constipation around week 2 so moved her onto kendamil comfort and it seemed to help settle her. Today she has been screaming during and after her feeds, straightening her back, sucking her hands, spitting up during burps and generally not being herself. She has also developed a rash on her face which we thought was baby acne. We’re unsure if this is the start of reflux or whether she has CMPA.