YOU SAID:

As he kept driving, he noticed that it was getting harder for him to breathe.

INTO JAPANESE

運転を続けるうちに、呼吸が苦しくなってきていることに気づきました。

BACK INTO ENGLISH

As I continued driving, I realized that I was having trouble breathing.

INTO JAPANESE

運転を続けていると、呼吸困難に気づきました。

BACK INTO ENGLISH

As I continued to drive, I noticed that I was having difficulty breathing.

INTO JAPANESE

運転を続けていると、呼吸困難に気づきました。

BACK INTO ENGLISH

As I continued to drive, I noticed that I was having difficulty breathing.