Whoa...I got my retirement orders April 2014, was granted SSDI and started collecting it around April or may. So am I supposed to be paying for Medicare or something? What did I miss, I go to the VA for all medical stuff.
The key answer to your question is: how far back did SSDI award your benefits? If they gave you back pay from April 2012 then you would be eligible for Medicare and thus need to be enrolled in Medicare Parts A and B.
I hope this helps.