My 5 week old DS has suddenly started breastfeeding for 10-15 minutes rather than 30-40 minutes they were doing before! I offer both boobs but he seems to only want each one for about 7 minutes. Sometimes he'll take one for longer but then refuse the second one. Is this normal?! I thought they were meant to get more efficient at around 4 months and I am worried that he's not getting enough. He's still doing wet and dirty nappies but his poos are smaller than they were before. Similar length (perhaps a bit shorter) gaps between feeds.