Medically undiagnosed condition: how to inform? I am currently a final year grad student. Sometime last year, I developed severe pain in one of my hands which led to a lot of time lost. I have seen some of the best doctors in the country for my condition (I am doing my PhD at a hospital so that helped) but we have not been able to narrow down on any diagnosis. Through out this time my supervisor has been super supportive and helpful; he even helped me arrange a few consultations. My PhD committee (which monitors my progress among other things) has also been mostly supportive. A few months ago, the pain began to subside (could be on its own, could be medicines helping). I communicated this to the committee members last month (who have usually been concerned and periodically checking up on me). 

A couple of weeks ago the pain is back suddenly and this time it is in both my hands. This has put me in a difficult spot work-wise and I feel that I might end up losing some more time if the pain persists.

Therefore, the premise of my question is: I have medically unexplained symptoms (MUS). In general people really have low tolerance for such conditions and often think "its all in the head".

My questions are:

1) How do I deal with telling my committee members that I am in severe pain once again? Given that I just told them last month that I was doing fine and that I do not have a diagnosis, I am afraid I might come across as someone using my illness as an excuse for reduced productivity.

2) I am due to submit my thesis in June. I am interested in applying for post-doctoral positions (most likely in Europe). Should I let my future boss know about my condition? I feel that it would be unfair to not let them know given that my pain can lead to (significant) loss of work time; however, since I do not even have a diagnosis I don't even know how should I go about disclosing it to them.

3) At this stage it looks like I might have to deal with pain on a long term basis. Should I expect discrimination (not legally, of course) in academia simply because I might not be as productive as other people? Any advise on how to deal with this kind of situation?

I have read some other related questions (for example, this) but I feel that my situation is slightly different given MUS.

Edit: I am currently doing my PhD in India
I think you should inform your thesis comittee about your current situation. Best case, they are understanding, worst case they will ignore it for PhD-related matters. It might help to get a sick note from an independent professional even if the diagnosis is difficult. 

As to your second question, I would suggest to not disclose any health issues in the hiring process for the same reasons as stated in your linked questions, unless the position is specifically advertised as 'disabled applicants preferred' which I believe is a thing in Germany, for example.

Regarding your third question, I cannot say in general whether discrimination is to be expected. Depending on your condition and country of future employment, there may however be laws in place to protect you from discrimination against your condition.
I can only offer limited advice on how to deal with discrimination otherwise, but coping strategies against pain may be of interest to you in case of chronic problems, and may be subsidized by (potentially employer-paid) health care.