YOU SAID:
i cant believe you are wearing that
INTO JAPANESE
あなたがそれを着ているとは信じられません
BACK INTO ENGLISH
I can't believe you're wearing it.
INTO JAPANESE
あなたがそれを着ているなんて信じられない。
BACK INTO ENGLISH
I can't believe you're wearing it.
That didn't even make that much sense in English.