I wonder what it would have been like if we dated back in high school/ college.
I wonder whether we'd still be together if we dated back then.
I wonder what it would have been like if we dated back in high school/ college.
(高校／大学時代に彼と付き合ってたら、どんな感じだったんだろう）
I wonder whether we'd still be together if we dated back then.
（あの時付き合ってたら、今頃まだ続いて（付き合って）たのかな。）
＊date=付き合う
＊back in ○○ ＝○○の時／○○時代
（アメリカでは大学時代の事を話す時は、通った学校が ”University" であっても”college” を使うのが一般的です。大学生なら “college student" 等。）
＊back then = あの時
（この前に "then" が何時の事なのか話してある前提です。）
お役に立てると幸いです(^^)
I wonder what my life would be like now if I had dated him when I was in university.
I wonder how my life would have turned out if I went out with him during university.
この場合、次のような言い方ができますよ。
ーI wonder what my life would be like now if I had dated him when I was in university.
「大学時代彼と付き合っていたら、わたしの人生は今どんなだろう」
ーI wonder how my life would have turned out if I went out with him during university.
「大学のとき彼と付き合っていたら、私の人生はどうなってただろう」
ご参考まで！
日本 
カナダ 
