Hi Amy Duncan,
First you try by deactivating unnecessary plugins[Especially plugins that regenerate thumnail of your post ]. If this does’t help you out then please provide us your login details (FTP and WP-login details) so it will be easy for both of us to find the solution of the problem as soon as possible.
Note: Please take a backup of your site before proceeding. Normally we use duplicator plugin to make a backup. https://wordpress.org/plugins/duplicator/.
and send us your login details through this email address: [email protected]
Here is the video tutorials how to use duplicator and save it to your local computer https://www.youtube.com/watch?v=VdvOGV2eIjE