Can I ask a premmie question???

My DS is almost 13 weeks now but was 8.5 weeks early
Now he feeds but is sooooo slow to feed (can take up to an hour to feed him). I call it lazy feeding. And sometimes he will only drink 100ml.
The heat we r having here isn't helping but I just wanted to know if its a premmie thing to be a lazy feeder or if I should be concerned