Why am I NOT high risk?

I had my annual mamo a couple weeks ago which showed "possible abnormalities". Yesterday I went in for more mamo pics and an ultrasound. Nothing was seen on the new mamo pics. Two areas were seen on the ultrasound although she told me that it's not the same thing they saw on the first mamo. So, the doctor is "almost positive" these are firbroadenoma and she recommends waiting 6 months to see if they change.

This is were I'm confused . . . I'm 43. My sister, who is now 50, had invasive BC diagnosed when she was 41. My grandmother also had breast cancer. Because of my family history, I would assume that I would be considered high-risk, but they say that I'm not. I have read that fibroadenomas can be confused for cancer from ultrasound pics, so I'm surprised by the doctor's recommendation. Also, it's more common for a younger woman to develop fibroadenoma. And, I read somewhere that fibroadenomas are usually 1.5cm at least, and the larger of my two lumps is only 5mm! Despite what she thinks, I am having them biopsied in a couple weeks.

I told myself that I'm not going to worry unless I have to, but I can't help it. Everything that I read tells me this is NOT fibroadenoma:

It's much smaller than 1.5cm, I have a very close family history, and usually younger women get firbroadenoma.

Can anyone give me some opinions?

Thanks for your reply, Lanie.
They said that there's a "formula" that they use after asking some questions to determine whether women are high-risk. Supposedly, it also has to do with the age of your first period (mine was at 14), and first pregnancy (mine was at 23). In any case, I don't trust this "formula" they use.
I did ask if it would be the same doctor doing my biopsy that did my ultrasound, and it's going to be a difference doctor, thankfully. I didn't like the first doctor, because she made it sound like it was impossible that I had breast cancer. Before she did the ultrasound on me herself and after she looked at the technicians ultrasound images, she came in and said, "Well, I didn't see anything on the images which is what I expected". So, because I'm not what you consider "high risk", you don't expect anything? Not that I want cancer, but I want a doctor to expect breast cancer and to really, really look for it. That's a doctor that would be better safe than sorry. She was assuming. Based on what? I don't know. Ugh!

Thanks Lanie ~
I'm not too worried, just a little. Thanks for your advice and well wishes. I'll let you know how it goes after the 17th. :)
Brenda