What Could Cause Missed Periods After Being On Provera?

Hi, I am 42 years old and had irregular periods ever since I first gave birth at the age of 25. Both my kids were born thru G-sections and they are 7 years apart. I have missed my period for three months now and my last period was on the 19th oF Dec 2010. I had all the symtoms of a period coming like backache, stomachaches, pimples outbreak and swollen breats but no sign of it and have even taken provera to induce my periods. I hv done a pregnancy test last month and it was negative. would like to get an opinion before going to see a gyne. Thanks