Fibromyalgia why is it so hard to be seen as being ill?

I applied for PIP Dec last year. But GP only confirmed fibromyalgia diagnosis in Feb. 
I was fit and healthy until RTA caused a spinal injury 9 years ago but with physio and meds I was back working after 4 yrs. The medication I was on helped me keep going.  But after 7 yrs the gabapentin and tramadol was stopped. 
Don't know how your GP's are but my practice was reviewed meds for most of the long term users.
POINT my sister has MS which was diagnosed in 2000 but back in 2017 GP told her that her gabapentin was for her use and she could not sell it. I have the same GP.......
I tried and tried to get pain control restarted but the withdrawal symptoms had taken over. 
And still I worked through this.. Own business so working around 70hrs a week but chronic pain was always there. I have to be honest but until I was diagnosed with fibromyalgia I had not really heard of it. All GP would say was the road accident had caused nerve damage and the pain I was feeling was not real.
I've been through years of hell without any pain control, had lost all trust in the health care system (  and me  an ex nurse ) . It is hard to remember but it finally got to the point I took an early morning walk to the river, watch the sun rise and just walked in. I just wanted the pain to stop and I could not see any other way to make it just be gone. That has the lowest point but I had just given up looking for help.
I had all these symptoms and with my background I had diagnosed myself in my head. I'm now in my 50's so could see many more years of pain ahead. I nursed many patients over the years and when they were ready I made them one promise... pain management was always there.
I not saying the pain I suffer is worse than anyone elses. We are all different, we have different stressor, different tolerances to pain, and for the lucky ones, a support network that really does help. I don't know if it's because I was the care giver that I am struggling to expect that I am the one needing care.
There are millions of fibromyalgia sufferers out there but I feel stuck where I am.  I lost my business due to this illness, I lost my self respect when I attended the face to face PIP assessment. I was refused PIP with zero points on the assessment and the reconsideration and was told apply again, second go zero points again.
I step out the door, someone asks how you are and it's automatic to say fine. I think it is ingrained into us, I honestly don't think anyone wants to hear how I ended up crawling to the bathroom because my muscles had gone into spasm and I had fallen. Or how I am dealing with the fracture rib  without painkillers.
Most days if I managed a few hrs sleep I still wake so numbingly weary, my limbs feel weighed down and I think myself lucky if the bone deep pain is not there. And for pain control ..... Over the counter co codamol, not great when taken if you have IBS  but that's what doctor prescribed.
I'm still living with daily pain that can have me screaming if it takes me unaware but I was looking into a few alternative therapies to help but these are not provided by the NHS.  I now need to go back to my GP and ask again for stronger painkillers. 
I was starting to look to the future again, looking past the pain. One step at a time well I had taken a hugh leap forward expecting PIP payment could help provide and pay for the alternative therapies to help me cope. I have gone through the withdrawal symptoms of prescription medication once and I believe my GP will be uncooperative with stronger meds. For the last few months I felt I had some control again with plans to take my treatment forward but that just won't happen now. All I have left is this tribunal that will decide if the care my youngest daughter gives is actually worth anything. Her college work suffered and she eventually failed her course because of me. She is twenty and is stuck at home with me most of the time. We do have trips to hospital if I need stitches or need x-ray or appointments. I know part of my illness is the fogs but it feels at times I am losing my mind. I forget things, lose things, leave pots/oven on, leave taps running for bath. It's not the future she had planned for but I don't know if she feels stuck with me. We have worked this illness into our life.... If the pain or gigging effects my mood she usually now sends me to my room. It is actually safer that way as my sudden tempers were getting nasty. My world is now limited to my garden and the small box bedroom. I don't expect any replies but just need to know I'm not alone with my struggle to get help. Stress itself is a trigger for fibromyalgia just like many other illnesses but the process of meeting the PIP criteria does not help but I have found is making me feel worse. Good days, bad days, I don't know how you all feel but for me all days are bad days. Nine years down the line and I still want to be able to do the things I did before the accident. I want to see that person again, to know what it is to actually have a pain free day.
When I was a kid I sometimes heard my Granny say  " there but for the grace of God go I" . We don't know what is around the corner but at present I feel everything coming at me is there to bit my a***.