@littlek,
My friend who has had two different breast cancers had dense breast tissue (also poly-cystic which appears to be another risk factor) which is how I know about it. She likely has the genes for breast cancer, though, .
You and I are both also at higher risk because of not having had kids and breast fed young.
(I don't have dense breast tissue, though.)
Alcohol intake is the only other risk factor you've not mentioned...it also increases risk.
I'd also be staying away from meat pumped full of hormones and such...which a lot of chicken is, and I think a lot of your other meats are, too.
Other than that? Have your MRIs.......and try not to worry.
SOMETHING is gonna kill you no matter what you do.
I was brought up to believe I would almost certainly get breast cancer because my mother died young from it. My GP advised me to look into prophylactic bi-lateral mastectomy, and I did, and was reassured.
But I guess I learned to be relatively philosophical about it all fairly young, although that was a hard and nervous road.