I feel the same except im 17 and a half
I have no idea what im gonna do when i turn 18 and suddenly have a million more responsibilities and cant even handle life with my parents doing evrrything for me. I try to just ignore it
Sorry this post doesnt help at all but just wanted to give support youre not alone i think its normal to have anxiety surrounding the future and aging even for people without anxiety issues. Just tell myself in the long run it will be fine and once i am an adult with experience i will know how to handle things since problems always seem smaller looking back yknow