Withdrawal symptoms are truely terrible...I don't know how gradually you stopped, but it should have been over three weeks, with the last dose being the smallest possible every other day before you stop...if you didn't do that, then try to take smallest dose you can take every other day, along with klonopin, and when you withdrawal symptoms stop, then keep it up for one more week, then stop.
also i don't know why I decided to do this to myself right now...so i'm going to start taking celexa again in the meantime for a while. Maybe my body just isn't ready to come off it yet. Panic attacks are not fun!