Can I revert my form to a previously saved state?

I had created a form with various form fields & conditions & have now gone back to the form & it's all blank...Is there a previous / earlier version we can restore to? How does this happen?

Though I am not sure what caused your form to be blank, you can always restore your form to a previously saved state using your revision history:

http://www.jotform.com/help/294-How-to-View-Form-Revision-History