Feeling of loss I can't shake

I sit here awake past 4 am wondering when I will feel the "joy" overcome the pain due to the loss of my Father? Eveyone tells me that I will recall better, happier times and reflect on positive memories. So far they are wrong. I am haunted by hearing the diagnosis of a rare cancer, the extreme efficiency the cancer did it's job, the shock of him opening the front door half the size he was when I saw him before and the lack of compassion I saw in the healthcare providers who knew he was "terminal" and kept him at arms length. I want to remember the happy times but can't shake the harsh recollection of the last 120 days of his life. I am so afraid to take a deep breath at times as it feels as if the pain will crush my lungs just as it crushed my heart.