If you can live with it on your concience:

1. Edit level.dat with NBTExplorer

2. Expand the "player" tag and change the value of playerGameType from 0 to 1, then save

Supposedly that would work but don't take my word for it.

Thank you soooo much i am gonna try it. i dont care about my conscience as much as i want my diamonds

and if it fails i am just gonna /gamemode creative when  i respawn and get my stuff back

Just turn on keepinventory

or...

just copy /gamemode creative to your clipboard before going into game. 

Then, as soon as you load the world again, type T (or whatever the chat button is) + Ctrl+V. Gotta be fast to prevent the death from occurring...

@kelvinhall05 Can i do that outside the game

@TopHatProductions115  only problem is i am at half a heart and i know i wont have enought time

Yes, it had to be done outside the game. You're just editing the world file.

this one, right?

set to true?

I guess but you'd still die. You would keep your items tho.

Changing playerGameType to 1 will make it creative tho. Read my original reply.

i did, i am loading up mineraft now. thanks for the help. i will tell you if it works

update: thank you soooooo much it worked

oof - not enough time for 4 keystrokes  Should have smashed pause at 2 hearts...