Recently learned of my mother's Stage IV cancer

I know so many stories here are similar.  My story, I suppose, wouldn't be much different.  But I feel a great need to tell it, just to be heard, to have fellowship with other people who have gone through the same thing.

My mom only recently told me that she had felt the lump in her breast for over a year now.  Only recently did she finally have insurance, and so when she visited the doctor, it was so obviously cancer.  And then over the last few weeks, it seems like there's just been nothing but new bad news.  After the knowledge of the breast cancer, it was discovered that it was in the bone.  Then, while rolling over in bed, there was a pop in her rib - as though it had broken.  It hadn't, but there was definitely bone loss.  Now the whole rib cage is in pain.  The cancer's also in the spine.  It's, of course, Stage IV.  She's been advised not to perform her old job any longer.  She's already on a bunch of new medication, and the chemotherapy comes soon, I'm sure.  She'll be given medication through an IV at some point. 

 I'm just baffled at the speed at which the bad news comes forth, and I'm always scared of what comes next.  Mom has cried very little in front of me and says, "I've already done all my crying."  Last night was when I really cried.  I've seen that cancer has hit people much younger than my mother, but my mom still just seems so young (though, she's in her mid-50's).  She's always been so strong, was always a walker and a runner, worked so much with her hands, and I've never envisioned her as a weak individual.  It breaks my heart to see her hurt, to hear that she has to take so much medication, that she'll have to spend so much time inside hospital walls. 

 When I was an infant, my mother actually had to leave my dad and me to go take care of her mother, who was dying of lung cancer.  I didn't ever think that there may be a point where I'd have to play caregiver to my mother, the way she told me she was caregiver to hers.  I also didn't really remember until recently that my great aunt on my mother's side also had breast cancer.  As I continue to think about it, I'm almost diagnosing myself with cancer before I've been formally diagnosed with it.  I think I'm lucky, because I know what to look for now, and now I'm constantly thinking to be looking.  But I fear that I've been thinking so much that I'm going to let it dominate my life.

 At first, I was really mad when I heard my mom had known there was a lump a year ago and didn't do anything about it.  But I can't say I entirely blame her.  For one thing, she'd had lumps a lot while I was younger, and that's all they ever were - lumps.  She'd had all those removed.  What if she'd had this one removed?  Might we have gotten rid of it before it was cancerous?  Was it always cancerous?  And she didn't have insurance at the time.  The economy was terrible to her, she was stuck in a home she didn't want to be in, and she couldn't get out.  How can I be mad at her for that?  And there's nothing that can be done about it now.  Now we're here, and all we can do is work from where we are.

 Surely, I'm not the only person who's gone through similar feelings.  Confusion, distress, fear, even when you aren't the one directly affected by the cancer itself.  I wasn't there for my mom enough before.  I definitely won't let that continue now, not when she needs help the most.  I regret so much of my behavior toward her in the past.  I just want to be with her now.

 I guess I don't have any real questions or anything.  I just needed a group of people to talk to about this, who understand this from the same perspective I'm seeing it all through.  If that makes any sense.  Thanks for reading, and I'm praying for everyone here.