'I just don't know what else to do when I can only manage an hour or so a day pretending to not be desperately sad and struggling'
Sign on, and get a GP/consultant to back you up- if your current one isn't good then change them. Go back and tell them how you're feeling, so they can try something new. You can always do some voluntary work or something to help yourself if and when you feel like it, and gradually build up to work as you feel able.
For now, you should focus on your health, get help etc.
You must know that you're unable to work full time partly due to trauma, but you've picked basically the job most likely to lead to someone having traumatic experiences? It's only a matter of time before a client does stuff you don't like etc, something really bad, on top of the possible general trauma of the job.
At the moment your MH is such that you'll probably be eventually able to work again. But now imagine you endure violent rape or something else in your line of work- how fucked up would you be, to have experienced that on top of your current problems? It'd be much harder to come back from- you'd be a complete wreck.