Excessive Site Size

My hosting service says my site is over 16G — it is an ecommerce site running woocommerce with a blog and maybe 100 products. I see that there are a lot of copies of images in various sizes that are generated by wordpress. There are also a lot of unattached items.
What is causing the site to be so big? I have other sites running wordpress (not ecommerce) that are about 3 – 4 G, so I am thinking that it is not wordpress itself that is so big.
I have tried searching for images in posts, products and pages, but the accuracy rate is maybe 80%. I don’t know how to identify unused images that are definitely not in use.

What can I safely delete without crashing the site or causing broken image links?
Also, if I get rid of all images other than the thumbnail, medium, and large, will this cause a problem?

Sorry if this is in the wrong place or if I am rambling. I don’t know what else to do at this point.
Thanks for any advice

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