Re: Getting approval from doctor for disability
Sorry to hear of your difficulties with navigating the medical and disability insurance issues.
Regarding STD/LTD, when you talk to your doctor to request their approval for you to stay on disability, it's a really good idea to give specific examples of why you don't feel you'd be able to hold down your job without getting fired, such as I'm too tired to do dishes or cook anything more than a simple meal, I get bad headaches on a daily basis, I have breathing difficulties about 2 times per day, etc.
In order for your doctor to keep you on disability, however, there needs to be medical evidence of your problem and the severity of it. Examples of medical evidence can include blood tests, xrays, MRI's, other types of imaging, or other medical tests that aren't subjective. Regarding the severity, I agree with the other poster that they will look for evidence of your inability to work, such as frequent doctor appointments/hospitalizations/tests, etc.
The DI carriers really are a pain to deal with - they will call you at least once a month and ask when you plan to return to work, and they will regularly send you paperwork that you and your doctor have to fill out to show you are still eligible, and they will get your medical records regularly. If they see an opportunity to get you off their policy, they will try their hardest to. Be prepared for this and fight for the benefits you need and deserve. Get copies from your employer of the STD and LTD policies that were in effect the day you last worked, as you will likely need to refer to them to understand your benefits and rights.
It would also be a good idea to file for SSDI sooner vs. later. Approx. 20-25% of people get approved at their first application, so you might get lucky or you might have to wait for a hearing in front of the judge where most people get approved. The process takes a long time and it's best to start the process as soon as possible in case you aren't able to return to work.
I really hope you can get your condition under control and get back to work, but it's a really good idea to prepare for the worst. My LTD DI carrier forced me to apply for SSDI and I thought it was ridiculous at the time as I really thought I'd be going back to work as soon as my back healed. Six spine surgeries later I now know I won't be able to return to work and am really glad I have SSDI.
Regarding getting Medicare, it's 2 years and 5 full months (they start counting on the 1st day of the month after you last worked) from the date you last worked. That's another reason to get going on your SSDI application, so this date won't be delayed should you need Medicare.