It seems to me that Femara perhaps failed to work for you in the long run - which I myself am all too familar with.  I was on Femara after I had a mastectomy and finished chemo 3 yrs ago.  While I was undergoing breast reconstrruction earlier this year I learned that my plastic surgeon found suspicious looking tissue within my chest wall.  It came back positive for cancer.  It was exactly 3 years to the date and in the same spot.  Very devastating to be 34 and have cancer twice in 3 years.  My doctors seem to think that one little tiny cell had been left behind, and despite being on Femara, that little cell grew slowly over the last 3 years till it was found at about 2cm.  I was lucky enough to have such a wonderful plastic surgeon who paid close attention, cause he said it looked like scar tissue but he decided to remove it anyway.  His caution saved my life. 

Like you, I've had routine blood/marker screening test over the last 3 years.  None of them produced any meaningful results or findings.  I don't know if maybe things were too small to be detected or if it was a case of false reporting.  No one really knows how or why these things happen.  Personally I have stopped trying to figure out why, and just go with the flow.  My reconstruction is now on hold as I go through 35 radiation treatments that will be followed up with an adequate dose of chemo.  Since I missed radiation the first time around I am hoping that it will help to ensure this round is successful and prevent the cancer from ever returning.

Good luck to you.  I hope you get some answers and get back on the path to being "cancer-free".

Angi