Sidebar not displaying

The sidebar is no longer displaying on my blog. I have not made any changes to wordpress recently. I have only been posting content. This has been happening for about a week now. Initially it started when I added a new post via email. Then the sidebar, and only that post would display. I found that by deleting that post, and then re-adding it, the sidebar as well as all of the other posts would display. Now I cannot get the sidebar to display at all, as well as only about 6 out of about 75 posts are displaying. Any thoughts?
Thanks, Dave