Hi Eve,
There is no definite answer to your question of why you dad suffers so much. We all suffer once cancer knocks at our door. However, I would say that your dad shouldn't be in great pain if he is prescribed with pain killers and if he takes it regularly. If it doesn't work, maybe he needs to be hospitalized so that his pain can be properly managed. The psychological suffering can be more difficult to deal with at this stage and I can fully understand the traumatic situation your family is in. People here are very willing to share their experience and I think professional assistance from medical people is very essential. I don't know how old your parents are but you need to watch out the health of your mother as well.

Karen