My DS is 3 months old today. Since birth he has always fed for about 10 mins from one side and then not wanted any more. He feeds every 2 hours during the day and will go 5-6 hours at night with a 10 minute feed at 4am. For the past 3 days he's suddenly started feeding for an hour or more each time. If I interrupt him he cries for more. Last night he fed for 90 minutes in one go. Is this normal? I wondered if it was a growth spurt but during previous growth spurts he just fed more frequently but still for 10 mins each time.