Rejecting milk

Hi Mummies, my LO is 5 months old and recently has been rejecting milk. Used to drink 100ml every 2 to 3 hours but now only drinks 40ml to 60ml. That too will cry, turning side to side, refusing the bottle. LO is on full FM now. Weight has not increased and PD has requested to follow up every week on this. Any tips on how do i make my LO drink more milk?