Big trouble on my site!

I am totally locked out of my site. I have error that my theme support team have never seen before. They say I may have to reinstall wordpress, meaning I loose all the work I have done on my site since July. This is so upsetting. I am really really upset, as I have worked on this site every day since July 2nd, for at lease 4 hours!
This will put me out of business. Is there anybody who can help me please?
When I go to my site I get this error message:
‘One or more database tables are unavailable. The database may need to be repaired’
But there repair does not work?!
I am desperate here, please somebody help:-(