Can I lose my singing voice!?

When i was younger my mom said i had a really amazing voice (this was when i was like 8 or 9) and now (im 15) she said i need to work on it because it sounds nasally and she thinks i dont even talk right when i do? She thinks it sounds like im putting on a fake voice and im not. Can my voice really change that MUCH? because i dont think ive ever stopped practicing since i love to sing but i dont even think im good. Do you think its possible to not sign after being really good? or do i just need more practice and it will go back to how it was or at least get better? Thanks!