Not saving on Win10 Bedrock PC

hello mate, it seems to be every time i shut down / turn off my PC after playing Minecraft bedrock Windows 10 edition, i log back into the game and the thumbnail, title and world size all seem normal, just how i left it; when i spawn in, i'm back at spawn with the map again and everything that has been made has disappeared as if no progress has been saved since the very first start-up 

if i then exit to the title screen, the world still has the same name but the thumbnail is reverted to the spawn as i left and the world size has decreased immensely to >1mb

 
any help ASAP would be appreciated! - i am unable to play the game due to this