My ds fo the past four weeks has taken to pushing the bottle out of his mouth at every opportunity! He often does this after only 3ozs,he is 16 wks old ,then he cries and roots for the bottle I offer it to him the he pushes it out again.Then 10 mins later he takes it like he has never seen food!!Feeding time has become vv stressful,up to an hour every feed.Has anyone else experienced this ,and any tips,It's driving me bonkers as he is obviousely hungry!!