It is exhausting. And I feel terrible for him. He's soooo tired. It's been going on for 3-4 nights now. His typical day involves waking up around 5am, nap at noon (usually 1h30m) and bed around 6:30 or 6:45. For the crying, when it started, I went to make sure he was ok (there had to be a reason for all that crying, right?). I'd talk to him, feel his forehead, and notice that he stopped crying instantly when I was there. As more nights have gone on, I have gone in less. Last night I only went in once early on. When I go in and lay him down, he gets more hysterical (probably in no small part due to how profoundly overtired he now is). No teething that I am aware of at the moment. My gut feeling is that it's stubbornness, but I can't be sure. He is sort of an angel baby personality (so sweet and easygoing) except when it comes to sleep (which has always been difficult).