YOU SAID:

I've been going out with Nick Nelson since I was 14

INTO JAPANESE

14歳の頃からニック・ネルソンと付き合っていた。

BACK INTO ENGLISH

I've been dating Nick Nelson since I was 14.

INTO JAPANESE

ニック・ネルソンとは14歳の頃から付き合っている。

BACK INTO ENGLISH

I've been dating Nick Nelson since I was 14.