Hi Cyanbelle,
At your age I had the same feelings about my mom. I even told myself, when she dies, I would have to die also.
I'm twice you're age and my mom passed 2yrs. ago and I'm still here. I still grieve and miss her dearly, but I have a family now and I'm not alone.
As you grow older, you're life is going to change. You will have people around you to help you through the tough times.
Love and spend time with your dad now, stop thinking about his death.