My son is 8.5 months and had been sleeping through 12 hrs a night until 5.5 months. Ever since he’s been waking 1-3 times a night with a very rare sleep through. I’ve heard of sleep regressions but how long are they supposed to last? Any other ideas on why he no longer sleeps through? He’s also become difficult to put down at night when he used to be out like a light by 6.30/7