YOU SAID:

he is in pain and it will go away in a week

INTO JAPANESE

彼は痛みを感じていて、一週間でそれが消えてしまう

BACK INTO ENGLISH

He's in pain, and in a week, it's gone.

INTO JAPANESE

彼は痛んでる１週間後にはなくなってる

BACK INTO ENGLISH

He's in pain. He'll be gone in a week.

INTO JAPANESE

彼は苦しんでる１週間後には消えてしまう

BACK INTO ENGLISH

He's in pain. He'll be gone in a week.