YOU SAID:

I took my dog for a walk

INTO JAPANESE

私は私の犬の散歩を取った

BACK INTO ENGLISH

I took my dog walks

INTO JAPANESE

私は私の犬を散歩をしました。

BACK INTO ENGLISH

I was walking my dog.

INTO JAPANESE

私は私の犬を歩いていた。

BACK INTO ENGLISH

I was walking my dog.