Scared to death

I can't believe that after almost 12 years of my mother being diagnosed with breast cancer, I am sitting her yet again on a forum crying and scared for her health.  I was 16 years old when she was diagnosed and I sat at her bedside 24 hours for every procedure and treatment.  Though it was a tough battle, she conquered it with all her might of several rounds of chemo and radiation.  Lupectomy, follwed by a mastectomy of the left breast and 3 reconstructions of that breast.

5 years later, she was diagnosed with Thyroid cancer and yet again my mother fought that battle (a much "easier" battle though needless to say a heartbreaking chapter).  Again, that 5 foot 100 lbs woman beat that battle.  

2 weeks ago, she went for her yearly oncologist appointment.  He even said that after all these years once the lab result came back he was going to have her referred to her regular GP for further monitoring.  For one reason or another she had been wanting to but never got around to do the BRCA test.  Her dr. was discouraging and she replied, "I have 2 daughters and a granddaughter I am doing it for."  So the test was done.  A week later, I go home and find her and my father sobbing.  Truthfully, her yearly lab result had come back with radically high levels of her CA 27.29 serum (breast cancer marker).  Because she had thyroid cancer in the past, a part of the maintenance is to have thyrogen shots every 2 years.  This year was the year and it had been done the week before her yearly bloodwork.  The oncologist had the bloodwork redrawn and though the levels were lower, they were still high.  Thankfully, she just did a bone density scan today and passed with flying colors.  

 As of now, the insurance has approved to conduct a PET scan and is just waiting to hear from oncologist.  We are assuming early this week but in the mean time, we are a mess of emotions and I am personally terrified.  No one deserves such pain but I don't see how a person can keep going to battle.  I can't imagine what she is thinking and feeling.  

Does anyone have any CA 27.29 input?  I have read that it is not unlikely to have a false positive but realistically based on her history, how likely is that?  

 Oh and to top things off as mentioned earlier, I was 16 when my mom was diagnosed.  It was explained to me by my father at the time that she had a lump and it was only the lump being removed because thankfully it was early stages and the reason to remove some nodes was to make sure it had not spread.  Well this week when I finally had a private moment with my father the truth came out that is was stage 3 metastatic carcinoma.  As a parent now, I completely understand why he did it at the time, but because we all went through so much, my self and sister grew up fairly quickly from the experience.  All these years and not knowing the truth.  I literally had to walk outside I felt as though I couldn't breathe and was having an anxiety attack.  That very second just to think my mom was that sick.  I just can't take it!  I am a very emotional person but when it comes to these matters, I hold it all in and try to be the strongest I can for my family and break down on my own.  

I have no other words than, I am terrified.  She is truly my best friend and though I have children that I dreamed of having my entire life, I really don't think I can survive without my mother.