I had a similar feeling at my mums funeral. I think it was more like an adrenaline boost. I had to be the strong one for my father and little sister.
The whole week I was busy with things, I even wanted to go to a party , just to get rid off my energy. So before the funeral, I was laughing and some people were offended because of that.
But after the funeral I felt completly empty.
You have to go on,life goes on.
And there are beautiful moments (the bright side), but you'll always miss her.
It's not just someone you love you've lost. It's your mother. And that can't compare to losing anyone else. (at least for me, unless... losing a child and that's something I don't even want to think about.)
Sorry guys for being so emotional.... hormones,you know.