So true - we tried out some formulas until we got the hint to try out goat milk formula. After little time her tummy got better. She just couldn't drink cow milk based formula as a baby now she likes to eat some yogurt and milk from time to time!
Don't panic, this is totally normal. Maybe you don't really produce enough milk and it is to exhausting for the baby - this could happen when you are under a lot of pressure. Maybe he just prefers the bottle :)
Also try to bump your milk and use formula in addition this should be a very balanced...