I changed my apple id and lost my notes!!! Is there a way to retrieve them?

If you were syncing Notes with iCloud, that should recover the notes. The iCloud sync is very, very slow, so give it plenty of time to sync.

If you weren't syncing Notes with. iCloud. do you have a backup you can restore from? Restoring from a backup erases all data currently on your device. Any data newer than when the backup was made will be erased. A restore is an all or nothing restore. You can't access a backup to see the contents and only restore certain files.

Backup - Restore your device from an iCloud or iTunes backup.    *

ASC YouTube for how to restore an iPhone, iPad, or iPod touch from an iCloud backup

ASC YouTube for how to restore your iPhone or iPad from a backup on your Mac

When changing back to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. If possible, also set up Family Sharing  between the IDs to keep access to your apps/purchases. 

 How to switch Apple IDs on your iPhone or iPad.      

How to transfer all files from one iCloud account to another.       

What to do after you change your Apple ID or password - Apple Support.      

Family Sharing.         

Family Sharing - Set up.        

Did you create a new Apple ID? If so, you can log in under the old one.

Did you change your Apple ID? Change your Apple ID - Apple Support

If so, all of your data should go with you.

Are your notes in a different email account?