I would suggest seeking out a 'psychodynamic' psychiatrist or psychotherapist for psychotherapy. You can get referrals by finding the nearest psychoanalytic institute or society. For example, in Wisconsin we have the Wisconsin Psychoanalytic Society; there are many more analysts in larger cities. Analysis is very time consuming and expensive, but you would likely benefit from psychodynamic therapy at a lesser intensity, say about once per week. I do that kind of therapy, but it is expensive and so I don''t usually push it too hard. The only plan I belong to is 'multiplan'; there would be an 'M' on your insurance card, or it would say 'health eos'... if you have that on your card consider setting up an appointment in my office for telepsychiatry, which I do using a webcam.
The basic idea with psychodynamic therapy is that you have unconscious reasons for feeling as you do; you know some of the reasons, as you mentioned the cancer in your father. But something else probably set off this obsession with cancer, and the goal with therapy would be to be less controlled by your unconscious fears.
The best solution would be to have a 'real' person in the room, but if you cannot find someone and you have my network give me a call.
In the meantime try to open your mind to the idea that there is something under the surface that is scaring you. Sometimes that alone will increase one's insight enough to improve things.
I have taken cymbalta, and for me the side effects were not worth taking the medication and I have a close friend that experienced the exact same side effects. I gained 60lbs in 6 months with no change in diet. It noticed myself getting into habits where I would get on these wierd kicks. For instance, i had to have a baked potato every day for lunch. I would have very strange dreams that were waking me up every night and we I needed to urinate I would literally have to sit there for like 5 minutes before I would begin to urinate. I also take Klonipin and by far it has helped my anxiety better than any anti depressant has. Its also been something where I don't have addiction problems to. Not to say this will happen to you because everyone is different but I would deffinately pay attention to your behavior and syptoms