My 4 month old baby is staying awake for up to 7 hours a night before falling asleep.
We try to incorporate 3 naps a day, we do bathtime routine and he may fall asleep for even 25 mins but then he's wide awake and won't go back down.
I can spend hours and hours trying. Winding, feeding, putting him down. He laughs when I pick him up after he starts crying.
He is quite happy in those 7 hours - clearly shattered and is a really happy baby. He just will not sleep.
I am my wits end.
Please - any helpful advice. I'm so tired. 
(When he does go to sleep, he's a waking frequently through the night, he was previously sleeping 8-10 hours a night).