Feeling guilt is totally normal, I've been through the same experience and I personally never truly got over the guilt even though it's years ago? My mum didn't tell me she had cancer and I was too busy to visit her regularly etc I'm positive your dad wouldn't want you to feel this way. I was told, after my dad died that the more you love someone the more it hurts when they're gone, and I've found this to be true. I'm guessing your dad didn't tell you in the hope he was saving you from the pain of going through it with him, and I can see how in his mind this not knowing might help you but in fact it leaves you with too many questions that need answering before you get closure. All I can say is this feeling of guilt may never totally go away but it will get easier to live with, just remember how much your dad loved you, so much so that he didn't want you to know he was dying, trying to save you from such an awful pain. Try and talk to friends and family about your feelings as they are a good source of support. I hope this helps and I'm really sorry for your loss, regards, Graham