My DS is 7 weeks and in the last couple of days he has started to fuss a bit at the breast. He's feeding away and then starts to cry a bit. I am trying to get cracked nipples to heal so he has been getting one bottle of EBM a day to give me a break - do you think this is causing the problem? He has been getting bottles since he was three weeks old but has only started this crying business in the last few days.