Breast & Formula Fed

I give my baby mostly breast milk and maybe 5-8 times a WEEK I will give her formula , would my baby be considered a formula fed baby or still breastfed ? Also what is a good formula that doesn’t back them up, I have the gentle ease and I feel like she’s constipated, I can tell that she’s pushing and trying but nothing but air comes out. I know going a couple days without pooping is normal but it doesn’t feel normal because you can tell she’s pushing trying to relieve herself but cant 🥲