As you are already giving the feed on demand it may be over feeding..some infants have this issue of throwing up so try and give feed with the babies head held a little up..like putting a pillow under your lap..burping the baby is necessary

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<span style="color:#3B5998;"><b><a href="http://app.babychakra.com/article/1074">How should you Burp your Baby?</a></b></span>

; Hey please feed on demand three hours intervals atleast

<b><span style="color:#3B5998;"> @5f6e0b33c0de03004572c596 </span></b> I feed every 1.5 or 2 hours. And mostly it is on demand.