Have any of y'all ever switched formula without talking to the pediatrician?

My 6-week-old has been screaming, crying, arching her back all day and night now...she did fine on Enfamil AR, but when we switched to the Parent's Choice equivalent....we're almost done with the first container of it and she's just getting worse?? Everything I've read leads me to think that she might have a dairy issue...

Her doctor was out of town all last week and now we've hit Saturday night/Sunday morning. Doc knows all about baby's gas issues, but it's only gotten worse over the last few days. I got a container of Good Start Lactose Free and a bottle of pre-mixed Similac Alimentum...any recs??

We also got some of the old school Playtex bottles with the bag drop-ins, to try and cut down her gas even more (Dr. Brown's bottles somehow seem to make her gas even worse?! 😭).

Any help, recommendations, advice, etc. is greatly appreciated!! First-time mama over here and we are very tired and just want our baby to feel better (and sleep .she's even more exhausted than we are, of course).