reduce size of Wordpress wp-content folder

I have a Wordpress site hosted at firstumcsb.wpengine.com. My wp-content folder is so big (over 100 Megs) that I even had trouble uploading it to WP Engine.

I want to host it on a server with a local company (www.starlight5.com) and I have a version of it up there now (firstumcsb.org). Unfortunately it runs WAY too slow on that server and my guess it is because the Uploads folder in wp-content is too big because of multiple copes (in different sizes) of each image.

Are there any plugins or does anyone have any instructions on how I can locate which images (and their sizes) are being used by my website, and to eliminate the ones that are not needed? I would also like to make settings adjustments so that unneeded sized images are not uploaded or generated in the future.

I would appreciate any help. If you need admin access to the site, please let me know and I can provide that.

Thanks in advance.

Mark