YOU SAID:

he must have woken on the wrong side of bed

INTO JAPANESE

彼はベッドの反対側で目が覚めたに違いない

BACK INTO ENGLISH

He must have woken up on the other side of the bed

INTO JAPANESE

彼はベッドの反対側で目が覚めたに違いない

BACK INTO ENGLISH

He must have woken up on the other side of the bed