COBRA term

ody Q: My COBRA is supposed to end 3/31/2013. It is from spouses lay off. He turned 65 and began Medicare in December. Can child and I stay on COBRA another 18 months (for a total of 36 months) or does our COBRA have to end at the end of 18 months. I have been unable to find any kind of employment since 6/1/2012 and from 12/27/10 – 5/31/2012 worked part time seasonal, no benefits so was on his benefits. Child age 19 works part time, not in school due to anxiety. thanks for your help.