I'm no expert on suicide, but I don't think there is such a thing as suicide without pain. Just now I looked up suicide by painkiller overdose and it ironically sounds like a very painful way to die, like how a softball is hard.

Your parents shouldn't demand that you feel something that you don't. Saying "put on a happy face to your nephew's christening ceremony for God's sake. It's time for you to get over things. You can't keep thinking about the past forever" sounds very demanding and disrespectful. You should show and tell them how you really feel, as pisces22 said. When I first became depressed, I bottled my emotions inside for over a year before I broke under the pressure. As your parents, they should understand at least some of your pain. I am sure that they do love you and will try to help you.

I'm really sorry about you only having 10–15 years to live, and about your deteriorating hearing too. Mid 30's is too young to die. By the bye, what is this experimental treatment you speak of that you hope kills you?