milk strike!

My LO used to drink every 2.5h. Was fussing a lot and refusing to drink and changed the bottle brand recently and he started drinking better again. However now sometimes at 3.5h interval, he also doesnt want to really drink. Because of that he doesnt drink as much in 24h cycle and keeps waking up earlier in the MON to drink ? Any advice? What is the appropriate drink interval for 3 MO?