Advice for 3 week old

So here’s the thing ; I have a three week old, almost four weeks. She’s having a super hard time with gas & going potty. She screams and cries from the depth of her little heart. I’ve called her pediatrician & he says it’s normal. But she turns so red, screams, grunts, stretches herself out.. everything.. she’s had about six poopy diapers alone today.. they’re running & loose to the point where she now has a small diaper rash on her booty. I’ve been putting cream on her. I’m at a loss on what else to do for her. I wanna cry, seeing her in so much pain breaks me. She’s on Similac pro advance