My Baby doesn’t drink Breastmilk

Hi All, I have 5 mos baby boy. From birth till now, my baby is drinking EBM & Formula Milk (more to EBM) and it was okay till now. Suddenly, my 5 mos baby boy seems to enjoy the formula milk better by not finishing the EBM as he used to or getting frustrated when drinking EBM. I’ve tried giving him warm, normal & cold EBM, but still the same. While if its formula milk, he always finish and seems enjoying his meal. Anyone have similar experience? Note : he is teething now :)