Without knowing the details involved I'm going to say "sure you can sue anyone you want... but will you win?"
Did you sign the contract of your own free will?
Did you insist that your attorney be present, and yet sign it anyway?
If you didn't know what was in the contract, why on earth did you sign it?
Do you see a theme here... none of these things are your attorney's fault. Personally, if you decide to sue, I think a Judge would throw this out of court quickly, taking just a few moments to laugh heartily, first.