short feed times

Anyone else have short feeding sessions? This is my second and I've never had a baby nurse for long times. My 4 week old have never nursed him for more than 20 minutes total for both sides. Now he's eating for about 5 minutes on each side. He's gaining and healthy but I can't be the only one, right? Our pediatrician first asked if he was eating 20 minutes on each side. When I said no, she asked if it was 10 (at the time it was about 8) and I said yes.