Lost Posts

I discovered that some of the posts from both my blogs have disappeared out of the blue a few days ago. I realized they had vanished when the number of posts in my blogspot blog showed only 900+ when it should be around 1,050. When I checked the posts, they have indeed vanished from my blog. Has anyone experience this before? Could this be my computer has been invaded by some malicious virus? Gosh, this is scary. I really want to recover my lost posts, over 100 of them. Can someone tell me what's wrong?