HUGE ISSUE - Hundreds of pages keep getting recreated!

I seem to have a massive issue at the moment.

I recently logged into my Admin Dashboard > Pages and noticed that I suddenly had 171 Published pages and 202 Virtual pages!

When I clicked to view the pages, I noticed there lots of pages being duplicated (without a user associated!).

I've attached two screenshots of the Published Pages and the Virtual Pages.

My problems are this...

Why is this happening and how do I stop it?

I have a multisite setup (each site is exactly the same just different conent) and the attached screenshots are from one site. One of the other sites had nearly 7000(!) Published Pages - but I couldnt get a screenshot because the table of pages was empty.

Please help!

Note: The only pages which SHOULD exist have my name in the Author column (I believe 16 published and 4 virtual)

Images are too big to upload so here is a link: