3 small, painless, moveable lumps on my bottom gum on the inside, had them quiet a while my mum said it could just be normal, I'm only 17 will I die: (?

Yes. The only thing i know for sure as a dr is that you will die.But not soon from movable lumps on your jaw. This does however require a visit to a dr.
Fear not! Likely these are normal excess gum tissues or undulations. Cancer is uncommon among young people. Get checked by a dentist or a dr for reassurance. Google online for images of gums or buccal mucosa/inside lining of mouth. (perhaps u may die 60 years from now. God only knows!) in the meantime cherish and enjoy life with your family & friends ! god bless u!