Have you had a diagnostic mammogram, or just the regular mammogram. I also have dense breast tissue, regular mammogram gave me the all clear, it was an ultrasound that picked up tumor. Next mammogram they had to change all the equipment to do diagnostic one.
At my 1st year check up the place where I have my mammogram has a new mchine called tomosynthesis, this machine takes images in slices across the breast, is meant to be more accurate.
May be worth checking out if there is one anywhere near you.
All the best, but keep asking the questions if you are not satisfied.
I remember having breast pain, and was told it was hormonal.
Best wishes
Viv