I have a 4-week old and he has been feeding well and gaining lots of weight. For the last week I have found myself spending 3-4 hours constantly feeding in the evenings. Over the last couple of days he has started to get a bit grumpy and is waving his arms around and pulling off and then going back. Does this mean he is not getting enough? What can I do to stop the "fights" as he seems to get quite wound up. During the day he is fine.