Baby pooping too much ?

My little one has been pooping irregularly too much. She used to poop once every few days now she poops about 8 times a day. There was a day when she was given another kind ( but same brand) of formula and she was throwing up, returned to the normal one and then this pooping thing started. I think it may have be the cause and that I should switch brands now. Any suggestions or output on this ?