Help: Pages That I Didn't Create are Getting Traffic

When checking my stats this evening, I see two pages that I've never seen before have had visitors. Neither of these pages exists on my dashboard, nor are they accessible through any link on the front end of my site. Both of the urls end in words having nothing at all to do with my niche (one ends in nutrition, the other in dietitian). Had I not seen traffic for them quoted in my stats, I would never have known that either of them exists. I can, however, access them through the links provided in my stats and they do go to my site. One page doesn't have any content, but still features all of the links in my sidebar, as well as Google ads at the top of the page. The other page has a recycled paragraph from another page on my site and does not feature any Google ads. It gets even stranger, though, as the content on this second page appears to have 11 comments. Yet, when I click the comments link I'm directed to another legitimate page on my site. Any ideas about what's going on? I can't even delete the pages because they don't exist on my dashboard. I'm going to call my hosting company, but any feedback anyone can offer is also appreciated.

Thanks!