12 week old suddenly waking every 2 hours... advice please

[MYA2016]

Since 6 weeks my DS has been sleeping 8-9 hours a night without feeding, stretching to 10-12 hours in recent weeks.
He's breastfed
The last 2 nights he has woken every 2 hrs like clockwork from 10pm onwards and I'm exhausted. I know there can be a big growth spurt around this time but he's not waking up crying, just smiling and cooing although I am feeding him back to sleep as he won't settle without it.
Any advice? Do you think it is a growth spurt? He's not feeding any more really in the day that ive noticed
Any advice would be appreciated, I know I've been spoiled up till now but I'm already wondering how much I can take of this!

If he‘s just smiling and cooing, could you just leave him to it? Will he drop back off if you do that?

I would also leave him if he's not upset and hope he drops back off.

No I've tried that.... as I'm often lying there in denial that he can possibly be awake again! After 5-10 mins that's when the tears start. Also as soon as I start rocking him he becomes agitated as if to say what are you doing! It's only food that will get him back to sleep, but he is feeding for 10-15 min each time..?