Ive lost a major part of my world

Minecraft randomly crashed during my minecarting, and i was in the main part of my tunnels, and when i went back into this world, i spawned literally underground, suffocating, i dug up to the surface, my old house was here, my tunnel was there, so i went down it, most of it was intact, except, the main portion was only stone, i mined to where it shouldve been, nothing.