YOU SAID:
I wish i didnt eat my books yesterday
INTO JAPANESE
昨日本を食べなかったらいいのに
BACK INTO ENGLISH
I wish I hadn't eaten Japan last year
INTO JAPANESE
去年日本を食べていなかったらよかったのに
BACK INTO ENGLISH
I wish I hadn't eaten Japan last year
That didn't even make that much sense in English.