i need some help and advice for PIP assessment with capita please x

fibrogirl91

hey all im new here but im in desperate need of help and advice.
my pip claim has been sent to capita and they sent me a letter with a f2f assessment at a venue even though i stated on my claim form i need it at home due to my illnesses.
so my mum phoned capita and explained my circumstances to them and they were happy to change it to a home visit (i didnt realise that this was classed as me cancelling)
nobody turned up to my home visit.....
so my mum phoned twice on the day (friday) and explained no one had turned up...
she then had to phone back on the monday to see why no one had turned up....
she phoned back, they just said that there was a problem with the person who was supposed to turn up. they then booked me in for ANOTHER f2f assessment as a venue! my mum stated i cant leave the house and they said that there were no home visits available and that i would have to get a letter off my doctor to back me up (i have to wait up to 2 weeks for this letter) so my appointment at the venue is on the 21st of this month and they wont change it for a home visit due to there being none available apparently. they then told my mum that if i cant get the letter in on time before this appointment that i will have to phone on the day before and cancel the appointment resulting in them referring my claim back to dwp. and that i have to then phone dwp and ask them to refer it back to capita....
this is causing me severe stress resulting in my anxiety and depression getting worse and worse each day.
what can i do?
will i lose my entitlement to back pay if i end up getting awarded PIP? (if it gets sent back to dwp)
heeeeeeeeeeeeelllllllllllllllllllllllllllllllllllllllp