At 4 months your lo should be on the 4 Hour EASY, or close to transitioning to it.
I suggest following your lo's cues and see how you get on. When your supply is back, go back to the 3 hour, and then try again in a few days to the 3.5 hour and see how he goes. Once he is used to being back on a longer routine, you can transition him to the 4 Hour.
HTH
Good Luck and let us know how you get on.
Paula