Hi, my ex partner has control over my Icloud password.

If you forgot your Apple ID password - Apple Support Or

Change your Apple ID password - Apple Support

Hope this helps, best of luck to you.

Try changing your password.

For Problems With Your Apple ID

1. Forgot iCloud Password
2. Forgot Apple ID
3. Apple ID - Apple Support
4. Manage your Apple ID primary, rescue, alternate, and notification email addresses - Apple Support
5. About your Apple ID email addresses - Apple Support
6. Get help with Apple ID

After changing the password you will have to log out of your account using the old password. Then log in using the new password. Alternatively, call Apple and ask them to assign you a new Apple ID and password and transfer all your files from the old ID to your new one. You still need to log out using the old password and log back in with the new Apple ID and password on your device and computer.

Nothing unless your ex partner allows you to change it.

Not even Apple can help with that.