Formula advise


Today my baby girl complete 45 days. I've been partially giving her formula. To make it short I breastfeed her the whole day and give her formula in the night , so that I can catch up some sleep ( my husband take care of that ) . She take maximum of 2 formula bottles in a day. First we give her similac then she got diarrhoea. The pedi give advise to change formula brand to Nan HA. The problem is she got constipated and vomiting/ spitting a lot. So I've decided to switch again to Bremil ( because I've reading the post and if prebiotic/iron/ cows milk etc that would prevent constipation). I will start this tonight and I hope she won't have any problems. Any idea on the formulas? Love to hear your stories.