Sleep regression or what?

I know there are a million posts about sleep so bear with me. My son is 10½ months old and has slept through the night since 2 months old. We always put him in the crib awake and he puts himself to sleep.

Well the last few nights he won't put himself to sleep, he just screams until I come and get him. I have tried letting him cry it out but after 15 months of absolute screaming and sobbing, I just have to go in there. I've tried not picking him up and just calming him down and leaving. I've tried tylenol. Fresh diaper. But no luck.

No change in bedtime routine. He doesn't appear to be sick or not feeling well. I've had to literally rock him to sleep and try to put him in the crib asleep like I did when he was a newborn (and let me tell you, it's much harder when the crib is on the lowest setting and you're short!).

Anyone going through something similar? Any advice welcome!