Lin6 I'm so sorry to read about your experience. One of the many things that make cancer such an appalling disease, is that patients frequently have to endure all the side effects of horrible treatments without any certainty that it will work - and the disappointment when it doesn't is so upsetting.
As you have been on Tamoxifen, I'm assuming that your cancer is oestrogen receptive. On that basis I have a couple of suggestions.
(1) Are you sure your cancer is still oestrogen receptive? Cancer can and frequently does change it's receptor. If your cancer has become Her2 positive, that might explain why the drugs you have had, have not worked (because Her2 cancer requires Herceptin or Lapatanib). In order to discover whether your cancer has changed it's receptor your doctor would need to perform a biopsy of one of your mets. If you have any infected nodes this is a quick painless procedure - but a biopsy of the liver or bones is not painless or quick (but still worth it if it means you get appropriate treatment). My cancer changed it's receptor (it was strongly ER+ and became strongly Her2+), and the two Professors at my hospital said this is "incredibly common". I'm providing a link below to more information about this.
(2) It appears your treatment went straight from Tamoxifen to chemotherapy. Have you thought of asking to try an endocrine therapy such as Letrozole or Exemestane ? It's possible that your doctor didn't bother with endocrine therapy because they thought the failure of Tamoxifen indicated that your cancer was not responding to oestrogen deprivation. But endocrine tharapy works in a different way to SERMS, and people who have had no success with Tamoxifen frequently have success with endocrine therapy.
(3) Cancer that doesn't respond very well to systemic treatments does often respond well to radiotherapy (mine is like that). If you have too many liver mets for Cyberknife, you could discuss Tomotherapy. Tomotherapy is not quite as precise as CK, but it can treat many more mets, and bigger mets. The other thing you could discuss is radiopharmaceuticals.
Hope these suggestions help.
Link to study concerning cancer changing it's receptor
http://jco.ascopubs.org/content/early/2012/06/18/JCO.2011.37.2482.abstract