My 3-month old son has always been quite an easy baby, easy to soothe and easy to get off to sleep. He's sleeping well at night, with at least one good 5-hour stretch. At night I can usually just put him down in his cot after feeding and he'll go right to sleep. On that front we are very lucky!
In the past few days he's been fighting sleep before naps, becoming overtired and crying hysterically. Everything that usually gets him off to sleep pretty quickly - holding him and bouncing, swaying, squats, shushing, etc. just isn't working anymore. I'm making sure to watch closely for sleepy cues and at the first sign of a yawn or eye-rubbing I start trying to get him to sleep, but it seems he goes from wide awake to overtired instantly. Eventually after anything from half an hour to over an hour of crying he'll fall asleep and stay asleep for 2+ hours. Of course I have made sure that all the usual suspects are covered - nappy, hunger etc., it's definitely tiredness but he's fighting sleep so hard. He contact naps on me during the day because I want to avoid head flattening from too much time on his back.
Could it be teething? He's biting on his hand and drooling a lot, but I don't understand why that would only cause crying when he's tired, because he's perfectly happy and smiley during his wake windows. I've tried shortening his wake windows too, but until he starts showing sleepy cues he's just not tired enough to sleep, and the suddenly, bam, overtired and screaming.
Any insights please?