PiP Award Length

I have just received my PIP review award after sending back review at the end of September. Once again I sent in a pile of medical evidence. I have been given another two year award once again same as last time. I have long term medical conditions that get worse and used to be on indefinite award of DLA. This award is really a years award as they review a year early and will review again on 3rd December 2019. Bizarrely they stay in award letter they have 'given me longer award this time'. It's exactly the same. Two years and due for review next December. I  can't take it no more. I'm stuck in a perpetual cycle of medical evidence gathering and my GP surgery wrote me a stern letter telling me not to ‎ask for any more copies of notes or find another surgery as I am putting pressure on their secretaries. I am getting it from all angles and I dread asking every 12 months. I constantly have to keep re proving what I've already proved. What can I do? I've become so unwell constantly worrying about it along with other pressures in life.