YOU SAID:
i need his thicky dicky
INTO JAPANESE
私は彼の厚いディッキーが必要です
BACK INTO ENGLISH
i need his thick dick
INTO JAPANESE
私は彼の太いペニスが必要です
BACK INTO ENGLISH
i need his fat dick
INTO JAPANESE
私は彼の太ったペニスが必要です
BACK INTO ENGLISH
i need his fat dick
That didn't even make that much sense in English.