Almost everyone has some degree of the fear of death from the most devout to atheists. That your fear has become something of an obsession which seems to be affecting your daily life, I would strongly urge you to seek therapy to help you deal with your fears.
This forum is dedicated to anxiety and not theological debates about the afterlife. I would imagine there are websites where such discussions are at their core and with some searching, you will probably find people to help with your questions.
I wish you the best,
Hello,I am also 18 and experience death anxiety. Mine pertains to my health anxiety and a specific fear of dying alone and the process of actually dying, rather than what the afterlife does or does not hold. If you would like to talk about it feel free to stay in contact with me.