Saved world data inside the house I built, opening the world once again ending up dying after I suffocated from a wall.. I didn't even save my world inside a cave!?!

After mining, I went back to the house I built to clean my inventory and saving the game data. Saved and quitted the world like how it should be.. I opened the world once again ending up dying after suffocating in a wall, most of all, LOST ALL MY ITEMS THAT I WORKED HOURS FOR TO GET.. Now, I'm in level 0 AGAIN with no stuff in my inventory losing ALL the important stuff I kept there... I hope you guys fix this, cause I ain't playin' hours and hours to get all those stuff in my inventory just to get them gone.