YOU SAID:

I have Extreme pain in my backside.

INTO JAPANESE

私は私の背中に極端な痛みがあります。

BACK INTO ENGLISH

I have extreme pain on my back.

INTO JAPANESE

私は背中がひどく痛みます。

BACK INTO ENGLISH

I have a bad back pain.

INTO JAPANESE

腰痛がひどいです。

BACK INTO ENGLISH

I have a bad backache.

INTO JAPANESE

背中が痛いのです。

BACK INTO ENGLISH

I have a backache.

INTO JAPANESE

背中が痛いのです。

BACK INTO ENGLISH

I have a backache.