Can’t Log In after other disasters

Today my blog was fin until suddenly I went there and it was showing all kinds of php errors while saying my SEO database was being updated. So I disabled the All in One SEO plug in and the errors went way, but then my page came up blank. I tried to change my theme but it said it was broken and reverted to the default. Then I went to the posts because it looked like recent posts weren’t showing and it said I had none, but it listed all 590 posts.

Then it wouldn’t even let me in to edit any saying I was not authorized (I am the admin). I logged out and now I can’t even get into the control panel. What is going on and how to do I fix this mess?