DS is BF and then topped up with formula afterwards, he is 3 months old. He has recently been refusing the left boob at some feeds (yesterday at about 7pm, today at 2pm and 6pm). He won't latch on to it but screams with hunger. When offered the other boob or a bottle he munches away hungrily. There is milk there as I can hand express it. Any ideas what the problem could be?