Osteopenia

Since 2003, I have ben told I am osteopenic(?). I was put on fosamax at the time and had been on it until 2009 when I was abruptly taken off of it due to osteonecrosis of the jaw. Granted when you have pieces of bone coming out of your gums gets your attention, so now I take at least 1800 mg of calcium with D daily, I exercise, but yet my results of the bone density test do not improve. Some times the top number is higher or lower and vece versa for the lower portion. How long can you stay in the "penic" stage before it becomes the "perosis" stage and are the bone density tests even the way to go to track it? I get discouraged as I try to do wht is right as far as diet, but the discouragemnet plays havoc on me. Curious to hear what the community has to say. Look forward to replies. Thanks in advance.