I suffered with GAD for about 8 years - but I am almost fully recovered now. Just need to address a couple of issues and I will be fine again.
With regards to medication, I took pills for just over a year and did not feel any improvement at all - nothing. So I stopped. All under doctor's supervision and I stopped gradually. I can't really remember which tablets they were, it was about 5-6 years ago.
I know you are going to have CBT, but it may be helpful to visit this website that was set up by someone who recovered from anxiety problems. It helped me a LOT. The address is: http://www.anxietynomore.co.uk/
It is worth noting that I have a brilliant therapist, who I have been seeing for about 5 years. However, I think that the more knowledge you have about the problem, how it happens etc, the better - and the website I am recommending to you is really helpful. But a combination of knowledge, willingness to change, a humongous amount of patience, courage and a good therapist is the right recipe for recovery, in my humble opinion.
I hope this can be of some help to you!