you using the wonder weeks app? it might clear up some stuff
at 5 months we're at a point where some days hes getting a full 12 hour night
and other nights its start and stop over a 12 hour period
wife has him on a tight nap schedule which cleared up a lot of things
the biggest mind fuck fact is realizing that sleep is a skill and its essential for survival - its like the first building block of becoming a person and babies just do not have that skill down. its weird