Back dated esa claim 6 months

Hello ,im looking for any help or information please regarding my esa claim. I've suffered a bad breakdown over the last 6 months and basically let life and responsibilities pass me by, my doctor's whom I've been with all my life basically took me over the edge,it was imossible to get appointments close to the time of renting sick note date and then the receptinist said I'll put you down for a repeat sick note, I called a few days later to be told .sorry but the doctor wants to see you,so no sick note, and no appointment​for 4 weeks, anyways a long story which basically led me to not getting any money via esa leading to the worse part a breakdown .in this process before I hate the limit I'd put a written complaint in to my doctor's which ironically led to no reply but a letter stating I was removed from the practice because I'd missed 3 appointments. Totally untrue ,one I cancelled months before hand and renewed and 2 apparently with my diabetic nurse, which I know I did not make , but the nurse did , errm I didn't make the appointment. So now I've just registered with a new doctor , and I don't know if I'm entitled to get a 6 month backdated six note from them. Has anybody any form of advice please,I'd very much appreciate any information and help thank you