My iCloud storage is NOT full but I am getting full message

Pretty simple, you have 3.8GB of storage left on iCloud and your iPhone backup is 18.78GB. You need at least 14.98GB of space.

You either need to add iCloud Storage, delete data from your iPhone, or backup to your computer.

Upgrade to iCloud+ - Apple Support

See the following Apple articles:

Check your iCloud storage online or on any device

Check your iCloud storage online or on any device – Apple Support (UK)

Manage your iCloud storage

Manage your iCloud storage - Apple Support

How to use iCloud on iPhone

How to use iCloud on iPhone – Apple Support (UK)

Get help with iCloud Photos

Get help with iCloud Photos - Apple Support

Set up and use iCloud Photos

Set up and use iCloud Photos - Apple Support (IN)

See the following Apple articles:

How to back up your iPhone, iPad, and iPod touch

How to back up your iPhone, iPad, and iPod touch - Apple Support

How to back up your iPhone, iPad, and iPod touch with iCloud

How to back up your iPhone, iPad, and iPod touch with iCloud - Apple Support

If you can't back up to iCloud

If you can't back up to iCloud - Apple Support

A reset is different than a restore and will not erase your iPhone., How much free space do you have on iCloud, what size is your iPhone (128GB, 256GB, etc.) and how much space are you using on your iPhone (Settings > General > iPhone Storage.

You have a lot of photos. There are two excellent add-ons in ICloud +, first you get Private Relay which protects your privacy and avoids needing a VPN and 2 you can hide your email for certain sites.