I understand, i think, what you are going through. My dad died when I wasn't really expecting it and I went through a full grieving process. I expected to feel something similar when my mom died but it wasn't like that at all. Its been 11 months since mom's been gone now and I'm still waiting for it to fully hit me.
There is a component of relief but the fact is, with my dad it was somewhat sudden while with my mom, well, I'd started to grieve upon her dementia diagnosis and continued in various ways throughout her illness. Its called anticipatory grieving. Its not that you are not grieving now, its likely that you have been grieving bit by bit for a long time, and you are in a different emotional place that were you were when your father passed.
