I second pinkflower, you do sound depressed. It's possible there's an underlying medical problem contributing to (or even causing) the exhaustion and low mood. Did the doc who prescribed the anxiety med ever order blood work or other tests to check for such conditions? If s/he is unavailable, is there a clinic close by?

I'm not a doc and I don't know how things work in the U.K., but GPs hereabouts will check for common conditions such as hypothyroidism. They can also prescribe meds to help tide you over until you can get an appointment with a pdoc.

And as pinkflower said, please let us know how you're doing.