DLA to PIP

I have recently received a letter stating that I need to make an application for PIP as my DLA is ceasing.
I have been in receipt of DLA since May 2003 lndefinate. I have numerous chronic health conditions, Fybromya,ME Underactive thyriod, Osteoporosis,Blood pressure Cattecks on both eyes,i bowel and balder difficulties and Costoendrites.
With age all these conditions have resulted in very poor mobility and severe restrictions On my way my life style.
I was a Social Worker but due to memory and mobility difficulties as a result of Fybromyalga I have been on long term sick leave and finishing work.
My car is my lifeline and is funded by my DLA and support from family to enable me a quality of life.
After reading all the horror stories of other people's experiences and plus the fact currently apart from my GP and work who will support and clarify my difficulties I'm worried about my lack of medical evidence I still have copies of my original application for DLA where a doctor examined at home and told me then that there was no cure and that my mobility would worsen which is exactly what has happened.
I feel so anxious even more so after calling the DWP which I recorded as I found them very unhelpful in trying to register the claim..
All info that I have read suggests it's a tick box excersise and how you present no consiration is taken into , that disability can be invisible apart from my wretched wheel chair.
Are there any pointers that you feel are really relevant I have read and re read all the literature but still feel the DWP are on a mission to reduce or eliminate DLA payments even though I my application was accessed by a GP who had a very good insight on how my chronic condition would impact on my health long term.
Sorry for such a lengthy message but i fail to understand how therapists etc after a module on a computer can be qualfied to access various disabilities that all impact differently on all individuals without proper medical experience on so many different chronic health conditions.