YOU SAID:
i lost my dog and forgot
INTO JAPANESE
私は私の犬を失い、忘れてしまった
BACK INTO ENGLISH
I lost my dog and I forgot
INTO JAPANESE
私は私の犬を失ったし、私は忘れてしまった
BACK INTO ENGLISH
I lost my dog and I forgot
That didn't even make that much sense in English.