Categories not displaying correctly

[DebMomOf3]

I am at a complete loss about what's happened to my site and what might have caused it... As of 1am on Saturday (May 22), everything was working fine. The next time I visited my site that afternoon, none of my posts were showing up on the main page (everything else displayed perfectly) and when I looked in my dashboard - they were all there, but all said 'uncategorized'. Later that day the categories were back, and each post is listed in the correct category in the dashboard, but they still aren't displaying on the main page correctly. Some posts show up and some don't. There are posts from last December displaying on the main page, but one that I posted yesterday doesn't show up. I can't find a rhyme or reason as to why.

When I look at the 'categories' list in the dashboard right now, not all of the categories are shown. But when I look at 'edit posts', they all are categorized correctly and I can filter by category in that view just fine - all the posts are still there.

My site is www.momstakeonthings.com - you can see it best on the left side under 'Insteresting & Informative' - the most recent post that shows up is from May 6, and nothing between Nov 9th of last year and April of this year displays at all. There should be many, many more posts under that section.

My hosting provider has run a virus scan and that's clean - they also say there doesn't appear to be any malicious code or anything. I don't think I was hacked, but I don't know how this happened, or how to fix it. Please help!!