That being said, I think you need to discuss your fears with a profesional. If you don't, there's a real chance that you may end up losing out on spending joyous times with your Dad due to being too depressed to enjoy those special times because of being so consumed by your fear of losing him.
+1
Spend time with your dad and make some memories now when you can, sooner or later there will be a time when that isn't possible. Also, buy him a bike and steal his cigarettes.