YOU SAID:
昨夜、あなたのお母さんと一緒に寝ました!
INTO JAPANESE
昨夜、あなたのお母さんと一緒に寝ました!
BACK INTO ENGLISH
I slept with your mother last night!
INTO JAPANESE
昨夜はあなたのお母さんと一緒に寝ました!
BACK INTO ENGLISH
I slept with your mother last night!
That didn't even make that much sense in English.