I too had BC and a clear mammogram. My 6th sense sent me looking for answers even though a mammogram only 3 months prior showed nothing. An ultrasound cleared a lump I was concerned about, and found a small cyst that they weren't concerned about. Just to be safe they did a biopsy, and this cyst turned out to grade 3 invasive ductal cancer. A new mammogram still showed nothing. I have since had a bilateral mastectomy as I didn't want to fear every mammogram in the future. I also had an MRI to check the other breast which was clear. I decided to have the other one off 9 months after the first one. I have had chemo and will be on Femara for 7 to 10 years. Sue, like you I am glad I went with my gut feeling.
Chris