This is a user/peer support forum, which Adobe Support does not monitor. For account security concerns please contact Adobe Support directly. Visit https://helpx.adobe.com/contact.html, sign in, and then select the chat option.
In the meantime, I recommend you immediately change your Adobe ID password that you use to sign into the Lightroom app. Or if you use a social sign on method like Facebook, Google, or Apple, again you should change your password there, and then sign out and back into Lightroom. On Facebook, you may also want to go the extra step of removing Lightroom in your Facebook settings (you can re-add the the next time you sign into Lightroom). I have no don't know if someone else has access to your account, but changing your password is an important step in securing your account.
Is it possible you are viewing the Learn or Discover tabs? These are photos from other people that do not really exist in your account.
Is it possible you have purchased and imported Presets? Edit Presets are imported by importing images with edits applied, and of course these would come from someone else (not your camera).