Comments off and porn site addresses appeared

The problem is the ‘comment box’ closed on it’s own. And when i go to the admin page to rectify it, i found that when i go to >manage >code, i found that there were hundreds of porn site addresses together with my article. This was only shown on the admin >manage > code page. But if you go to the article on the actual blog you don’t see the addresses. And another thing that i found out was that when i copy the whole article from the actual blog and then paste on Word Document the porn addresses appeared together with the article. And even I re-post the article, it will happened again the next day. This has been going on for a few weeks now and on only certain or selected articles. Can you do something to block this from happening? Is that a virus/bug of some kind or some robots. Or could it be some people hacked into my blog? Its getting very annoying cause people cannot comment on these articles and furthermore if they copy the article and paste on Word they will see the porn addresses. Thanks. Anything I can do? Or how to stop that?