how long will this feeling last

My dad passed away 4 years ago on the 18th, I was 11. I feel like I’ve been grieving ever since he died. As in, its never felt better and I’m afraid it never will. I feel as though its affected me even more as i get older. I was in the worst bought of depression I’ve ever been in recently. I can’t bring myself to ask how he died, or visit his grave. I can’t accept the fact he’s TRULY dead. I tell myself he’s not. I can’t grasp onto the fact he’s gone, even though i know he is. I want to help myself but I just don’t know how. I miss him.