Can you explain the formula you are on and the teats please? We don't have Enfamil as a main brand in the UK, just the Enfamil reflux formula - is it a thickened formula you are using, is that why you are using the Y cut teats?
What is your day like at the moment in terms of?
Eat - what times, how much
Activity - how long for
Sleep - what times, how long for
Does he have any digestive issues like reflux? It is quite normal for an 11 week old baby to be waking twice for a feed during the night, especially if you have stopped feeding at 10/11pm - why did you stop this one? At 11 weeks I would expect a baby to have 5 feeds during the day, a dreamfeed (10/11pm) and one or maybe 2 nightfeeds.
Laura