One diarrhea a day?

My almost three month old daughter been having really really liquify mustard color poop for the past week... she poops once day or every other day for sure.. sure does so much where it leeks through her cloth... be fever.. she is active.. no crying or fussy at all.. drink her formula fine.. majority of

The time she is taking formula similac sensitive and few times a day she will take my breast milk... maybe I am giving her both my and formula milk, wonder if that will cause the diarrhea... I have been taking her doctor to for smallest reason from nail cutting to flat heads... all the time he said everything is ok..