Do you know how long you will have to wait for the CBT?
If the wait seems unbearable I would go back to the GP and see if there is any interim support available, maybe through the practice nurse if they have a mental health nurse there. You could also look up if there is a local Mind group in your area.
Nothing lasts forever, including the worst times of your life.. there will be better days. Just focus on the hour you are in and try not to be impatient with yourself.