YOU SAID:

if i hadn’t joined a gym

INTO JAPANESE

ジムに参加していなかったら

BACK INTO ENGLISH

If you didn't attend the gym

INTO JAPANESE

ジムに通っていなかったら

BACK INTO ENGLISH

If you didn't go to the gym

INTO JAPANESE

ジムに行かなかったら

BACK INTO ENGLISH

If you didn't go to the gym