formula question

My daughter has been on formula since 3 weeks old, she was drinking the similac sensitive pro for 4 weeks then yesterday I switched her to " gentle " by up & up .. she's pooped more with "gentle" then she did with the other stuff but she's been waking up almost every hour to eat which before she'd sleep for 3 hours between feedings, could the new formula not be filling her up ?? Or just a coincidence ?? Help please