YOU SAID:

When I was tired I fell asleep

INTO JAPANESE

疲れたときに眠りに落ちた

BACK INTO ENGLISH

Fell asleep when tired

INTO JAPANESE

疲れたら眠りに落ちた

BACK INTO ENGLISH

I fell asleep when I was tired

INTO JAPANESE

疲れたときに眠りました

BACK INTO ENGLISH

I slept when I was tired

INTO JAPANESE

疲れたときに寝ました

BACK INTO ENGLISH

I slept when I was tired