UC capability for work questionnaire

I have received my capability for work questionnaire for universal credit. It has taken me many many hours and have shed many, many tears so far, and am only now starting question 3! The guide is very helpful, but oh so long(!), and I am sooo exhausted and cannot concentrate and am really struggling with this, it's going to take me more time than I am given to do this. Is there anyone you can recommend who can help me with this questionnaire in my area (Cornwall)? I'm so terrified they will fail me and make me go to work (I haven't been well enough to work for 20 yrs!) and quite frankly the whole thing is making me very suicidal! I am very stressed about getting it right, but am at the end of my ability to cope with it now!
I was on ESA and DLA for many years, then I got married so due to my husbands wages no longer qualified for ESA. My DLA then changed to PIP, but they lowered my care rate to standard, and kept me on enhanced mobility.
My husband and I have now separated last month so am now claiming UC and having to go through this all over again.
After I got married and they stopped my ESA, they gave me ESA contributory credits, then out of the blue called me in for a medical assessment (which I was confused about as wasn't getting ESA but assumed it was for the credits) which resulted in them telling me I was fit for work, but then in the same phone call told me there were sorry but I didn't actually need to attend the assessment!
But the fact they told me then I was fit for work has me terrified now that they will say the same again, and I really have no idea how I would go to work?!
I have M.E, fibromyalgia, sjogren's syndrome, IBS, Lipoedema, Insomnia, depression and anxiety, etc etc! Just doing the form is severely exacerbating my symptoms, how on earth would I cope with working?!