Welcome to the site. I am very sorry to hear about your dad and I can so understand your feelings of bitterness and anger, that is common. I too lost my dad to this cancer back in 2009 and like you, I still think of him each day. You will indeed find so much emotional support here from people who can understand how you are feeling and what you went through, so keep coming back here and know that we are all here for you.
And also, I just wanted to say that I so agree with what Lainy said to you about Dr Giles and I think that he will be of great help to you. He can be contacted through this link here -
My best wishes to you,
Any advice or comments I give are based on personal experiences and knowledge and are my opinions only, they are not to be substituted for professional medical advice. Please seek professional advice from a qualified doctor or medical professional.