There is good research out there suggesting solid food isn't recommended till 6 months. Try changing the bottle? The Bare Air Free bottles by Bitty Lab. These bottles are helping my friends baby learn to latch and reducing gas/ spit up/ reflux!

This 4 almost 5 years ago, but it help my daughter keep some milk down. She was under weight from spitting up so much. She had acid reflux.

it didn't work for my daughter she still spits up tons !