I was diagnosed last week with osteopenia, the precursor to osteoperosis. I'm still awaiting the results of the bloodwork on parathyroid and vitamin d, but suspect they're ok. I am not a big consumer of dairy products so I am taking calcium supplements. I do know that the body will not absorb more than about 500 mg of calcium at a time. Are you taking the supplements all at once? If you are, that might be part of the problem.
I've started fosamax and can tell that may be a big rough, but i'll stick with it for now. There is also actinel which is supposed to be easier on the stomach. There is also a nasal spray that is used once a day, every other nostril. You should probably talk to your doctor about trying something else. I don't know about you, but it worries me so much when I think about not being able to do the things I enjoy doing because of this "thing".
I can relate to the low back pain. Try lumbar cushions and other supports for that.
Good luck.