Images not uploading/media image files are gone

I was unable to upload images (I’m a new WP user), and through a search on a help forum I determined that my image path was blank. After inserting ‘wp-content/uploads’ the problem seemed to be resolved, however, it was very temporary. Now, not only are the images not uploading, but the images in my media library are replaced by a box with a red x.

There are no new plugins installed (I only have three) so I don’t think that’s the issue.

If anyone is kind enough to respond, please keep in mind I’m a brand new user and am learning the basics and have yet to become familiar with code, etc., so please keep it as simple as possible. Thank you!