Hi Bea:  It's always very difficult deciding which treatment to try, so I would make a list of your concerns and ask your Dr if any of the meds you haven't tried would be contraindicated with atrial fibrillation and the gastric bypass.      Depending on what your Dr recommends, there's the option of Reclast/Boniva, which are a iv infused med for osteoporosis, Evista, Calcitonin or HRT. Fosteum is another natural treatment, if you would like to look into that.   Here are some links on the various treatments that you could read, that might help you in deciding what to do.    Reclast info from our Expert Dr Gonter: http://www.healthcentral.com/osteoporosis/c/73/13598/reclast-acid/?ic=4004   Reclast/Boniva info from our Expert PJ Hamel: http://www.healthcentral.com/osteoporosis/c/53591/49024/iv-stomach   Latest FDA info on Atrial Fibrillation with Bisphosphonates: http://www.healthcentral.com/osteoporosis/news-276007-98.html   Fosteum info: http://www.healthcentral.com/osteoporosis/c/76444/45257/osteoporosis?ic=4004   Good luck with this, I know how difficult this all can be, hang in there.