Hi Saffron5,
Me personally, I would tell them that your health has worsened, and how the changes are affecting you. You can do this by letter, so that you've got proof that you've sent it. However, they may not act upon it, until you actually have evidence to prove it. My thoughts are always - no harm in getting the ball rolling, and being prepped, however others may differ. I think it depends on your own experience., of which I'm sure some other claimants have had, and may respond to this post.
Regards, Chris
Nothing on this board constitutes legal advice - always consult a professional about specific problems