NW night - every 3rd night???

[Tecike]

DS2 is 5 mo now and for the past few weeks has been developing a strange habit... every 3rd night he wakes up every hour for a 3-5 min sh/pat. So, he has 2 good nights (is EBF, has a DF and a NF) then on the 3rd he wakes up sometime between 10-12 pm and continues waking every hour...he doesn't want to feed, just needs a few minutes of shushing and goes back to sleep. Last night I was so exhausted by 2 am, that I put him next to me, so I shushed him lying down instead of getting up to him. I noticed then that he had silent reflux each time he stirred. I know it causes him discomfort, it's the pattern that is weird to me - precisely every 3rd night?

Any thoughts on this?

[Tecike]

Our ideal day is:

6.30 WU (have to get DS1 for kindergarten, so it's kind of busy...)
E - 8 am
S - 8.30 - 10
E - 11.30
S - 12.30 (30 mins in stroller)
E - 2.30 pm
S - 3.30 - 5.00
E - 6.00
S- between 7.30 - 8 (DF -11ish, NF 4ish)

Now, this has changed the past few days, I think he's having a GS, so the first nap is 45 mins and I can't extend it, pm nap works if I manage to extend it (once out of three times, for the past 3 days) and last night woke up to feed 10ish after BT and so had an additional NF at 1 am...
Regardless of our routine, these strange NWs happened before the GS too... I decided to keep an eye on that 3rd day, to find out what we do different...