Shortening nursing time?

[nicolejshannon]

Is it normal for my dd to shorten her nursing time by half? She used to nurse 10 minutes on each side, but it's now more like 5-7 on side one and either that or less on side two. We are still nursing every two hours (sometimes more frequently) during the day.
She is on the low side for her weight (dr doesn't seem to be concerned) at 11-12 lbs at 4 months old and I've also dealt with supplies issues so I want to make sure she is getting enough... I was worried since she's not nursing for very long.