Formula feeding trouble

So my baby is 6 mo and I started giving formula at 2 months old. She’s always had this habit of constantly wanting to eat.

Like she DOES NOT have a routine with it, sometimes she’s okay for 2 hours sometimes she’ll eat 7-8 ounces in 2 hours

She drinks very slow, I tried getting the fast flow nipples but she doesn’t take it with the fast flow ones. Every little spare time I have i have one hand with a bottle in her mouth she doesn’t stop at all.

It would be so nice to have atleast a 3-4 hour gap between feeds 😭