iCloud shows that it is full but I am 100% sure it is not
Photo Stream has no impact on your iCloud storage. Additionally, iCloud storage is not just about your iCloud Drive - in addition to other data (e.g. Mail, Contacts, Notes, iCloud Photo Library, etc), your iCloud storage also includes any iOS backups you have enabled (i.e. from an iPod, iPhone and/or iPad).

If you have an iOS device, you can go to Settings > iCloud and check whether you have Backups enabled. While there you can also check what else is enabled.

In addition, you can also go to Settings > General > Storage &amp; iCloud Usage and then tap on Manage Storage at the bottom of the iCloud list. This will give you a breakdown of your data usage.