sort of like doing a "cleanse" or "detox." feed him all natural for a few weeks and get the original formula completely out of his system if that makes sense.
I would try just nursing and giving pumped milk as long as you can and taking him off of formula, then once he's been off formula for a couple weeks then switching which formal you're offering him.
If you want him to latch on its better for you to breastfeed instead of going on &off; with breast and formula but if you see that you're struggling with breatfeeding feed him the formula @ritamae
the only reason it's advised against is some women dont focus on keeping their milk supply up. if you give a bottle you're supposed to pump at the same time, so your body is being told to make the milk. if you don't pump when you give a bottle your supply will start to drastically drop.
you're able to nurse, pump and give formula too without any problems. you just have to remember to keep your supply up. :)