Thanks everyone

We tried mixing it and it slowly but surely worked. It's like she noticed it tasted different lol also try using a sippy with a soft nipple, the one we use is by munchkin

Did u try mixing lil by lil milk and formula I know wic showed me how with my 1st

And also, try the soft tipped sippy cups. They'll probably say like 6m on them, but you're starting a little late lol. (Not in a bad way because there's no set time your baby should be off the bottle) But don't be deterred because it says 6 months on it.

Does he eat solids at least 3 times a day? And have a snack once or twice a day as well?

Kinda. I guess the whole milk does not fill him up as well as the formula does. I'm even trying to switch to a sippy cup which is also hard to do.

I never did, are you having problems?