YOU SAID:

there must be a reason why your back hurts

INTO JAPANESE

あなたの背中が痛い理由があるに違いない

BACK INTO ENGLISH

There must be a reason why your back hurts.

INTO JAPANESE

背中が痛いのには理由があるに違いない。

BACK INTO ENGLISH

There must be a reason why my back hurts.

INTO JAPANESE

背中が痛いのには理由があるに違いない。

BACK INTO ENGLISH

There must be a reason why my back hurts.