VB - it is certainly possible to mix feed, but it is very important not to do this with a newborn. The only way to build up and maintain a good milk supply is to feed frequently from the start. Otherwise, your body shuts down the production line. Any bottles of formula in the first weeks will interfere with this.
This is not the same as saying 'you cannot breastfeed if you ever give your baby formula in the first weeks'.
But it is a fact - not my opinion, but a well-researched fact - that if you give breast/bottle alternately at the beginning, you are very likely to find you do not have any breastmilk rather sooner than you want to.
Exclusive breastfeeding has many plus points from the health point of view, but mixed feeding does retain many of the health advantages of bf, so it's worth doing if this enables you to continue....but not at first. It takes several weeks to establish a supply, and for some women, 50/50 feeding, even after a couple of months, undermines bf to the extent that supply ceases. I have seen this happen many, many times.
Sorry to be negative about this - if you want to use formula, then it's better to wait, and then keep it to a minimum when you do introduce it, until you are confident you have a robust and responsive supply.
HTH