Hopefully someone will be along soon and give you a more helpful response. I have not been diagnosed with secondaries, however I saw your post and did not want to bypass without acknowledging.
You say that you have just found out that it is most likely metastatic breast cancer. So you have not received a definite diagnosis yet? How are they intending to proceed as it sounds like things have been left hanging in the air for the time being and I would not think that is very helpful for you.
By the way, if you thought you had an herniated disc then I hope the. pain was at least adequately controlled. I can identify a little bit I think as I have. been having right side hip and leg issues since March. I got myself bone scanned and seen by Oncology in May. Got given the whole clear from bone scan. Eventually got MRI in August and was told it was prolapsed disc and not due to cancer spread just a few weeks ago. Still in a lot of pain though and still having niggles about secondaries being the cause.
It's not surprising that you are stunned and scared. Has it been some time since your primary diagnosis? I hope you have some personal support, someone you can talk things through with directly. I find it hard sometimes talking about my nitty gritty fears and worries with family etc. as I don't like to freak them out. I have found the helpline on this site helpful. Also, you may find it helpful to visit a cancer support centre like Maggie's, or similar if you have one in the vicinity.
Best wishes to you and a big virtual hug 🤗,
Chick 🐣 X