You did a mistake by not wearing retainers for prescribed period of time generally depending on severity of treatment the doctor will advise retainers for 6-12 months, there is also option of fixed retainers. But now in your case relapse of treatment has occurred means the previous treatment has failed so you need to get the treatment again.

You have to wear retainer mandatory for 9 months post braces treatment. And continue wearing it post that in your sleep at night. Failure of braces treatment happens because patients don't wear retainers