Yes, you need a certain amount of quarterly earnings credits in the last certain amount of years. For most adults, that means 20 quarterly credits earned in the last 40 quarters. Thus, you at least need to earn one more quarter now - by working an SS tax paying job and earning at least $1220 in 2015. However, it could be trickier than that because our credits scroll off the board of "recent work" - so you need to have analyzed which quarters, if any, will scroll off immediately, each upcoming quarter, because if you earn the one you need, yet another one scrolls off, you are still at "one short" to be insured. Worst case scenario, you need to earn 4 credits for the next 5 years. That is about $5000 over the next 5 calendar years - at a part time job. Earnings will reduce your SS, but only $1 for every $2 earned, so it would still be worth it, in my opinion. And of course, you will want to work only in a PT job that is not going to hurt your condition or be impossible to sustain based on your condition, or that is inconsistent with your asserted condition and limitations.
If you would like to discuss your particular situation more in depth, feel free to click on the "Affordable SS Answers" button above, and choose a consult arrangment that is best for you. We also offer a Pre-CDR Service that helps recipients of SSI or SSD maintain their ongoing claim in order to best present their case at their upcoming mandatory CDR.