Why does my icloud storage still say 5gb after deleting attachments from messages?

Hi , I've been having an issue with my icloud storage causing me to be unable to backup my phone and this is really important to me. My storage constantly says that my messages are taking up 5 gb but that's no where near accurate. I've deleted photos , individual messages & also vidoes and photos from within messages and Nothing has worked. As you see below the messages first says 5 gb and then says 96.1mb and this is causing me to be unable to backup my phone , seen below.