PIP ASSESSMENT query

Hello, I haven't used the forum before so not really sure what to expect.
I receive a letter with an appointment for an assessment dated 2 weeks form the day I got the letter. My form was completed by a worker at my local CAB on which she suggested I ask for a home assessment.

I phoned their (The CAB that is) helpline yesterday as was advised in the call to phone the number on the letter and ask them to change the appointment to a home assessment.
This I done but was told (in no uncertain terms) that my medical evidence had been assessed and I was deemed fit for a 'clinic' appointment. That if I wished to change this, I would need to get further medical evidence.

As it takes at least 5 weeks to get a doctors appointment on average lately. I have no hope of seeing my GP within the time span.

At present I am finding it very difficult to go out at all due to a flair up with my Diverticular Disease which means I need to be close to a toilet at all times. I never know how long these episodes will last or even what I will be like from day to day.

The stress of having to go through this process (change over from DLA unlimited award to PIP) is enough to keep me unwell so I am feeling really upset and anxious about the whole thing.

My application for DLA went to appeal which lasted for about an hour and left me feeling totally wiped out for the next few weeks.
I feel the whole process is now so stacked against claimants that it is keeping me awake at night.
Is there anyone who can suggest any options for this please as I feel I would manage so much better at home.
Thanks!

Thank you very much!
I was told that I would need a separate, very long address to forward information if I could get it from my GP.
Would they give me a fax number instead?

Contact the assessment provider and ask for a fax number.