Grieving boyfriend

Hi my boyfriend of 5 years lost his grandad who died of cancer on Thurs 4th April and hasn't been showing any signs of grieving, won't even talk about it. This is first time someone close to him has died since being together so i dunno what to do but he doesnt like to talk about his feeling much so I left him and told him I was here if ever he needed...
It is now 11 days later and he tells me it's his funeral in 10 days and still nothing, he seems in himself a lot and I'm worried about him and dunno how best to aprouch the subject...
I ask if he wants me at the funeral, he says he doesn't see why as I never met him but I want to be there for him as I worried about him....
I need of advice and help!!