YOU SAID:

i think i broke my back off a wall

INTO JAPANESE

壁で腰を折ったのだと思う

BACK INTO ENGLISH

i think i broke my back on the wall

INTO JAPANESE

壁に背中をぶつけて骨折したと思う

BACK INTO ENGLISH

I think I broke my back by hitting the wall

INTO JAPANESE

壁にぶつかって腰を折ったようです

BACK INTO ENGLISH

It seems that I hit the wall and broke my back

INTO JAPANESE

壁にぶつかって腰を折ったようです

BACK INTO ENGLISH

It seems that I hit the wall and broke my back