YOU SAID:
What will I do if I find out he cheated on me?
INTO JAPANESE
彼が私をだましているとわかったらどうしますか?
BACK INTO ENGLISH
What do you do if you know he is cheating me?
INTO JAPANESE
彼が私をだましていると知っているなら、あなたはどうしますか?
BACK INTO ENGLISH
What do you do if you know he is cheating me?
That didn't even make that much sense in English.