Lump On Left Breast. Ultrasound Said Heterogeneously Dense Breast Tissue Seen. Worry?

I have a lump on my left breast. 6 months ago they did a ultrasound and on the report it says: Findings: Real-time ultrasound examination of each breast fails to rveal any solid, cystic or complex mass. Impression: Benign bilateral breast ultrasound . If a mas remains palpable, alternate imaging modality shoud be considered. BIRAD 1 Negatie Annual mammographic is recommended. Last Monday I went to see my Dr. and had him check the lump again. He said he clearly feels it and sent me for a mammogram and to see a breast surgeon. I did the mammogram and the report says Findings: Heterogeneously dense breast tissue seen, bilaterally. This finding my decrease the sensitivity of this study for evaluation of underlying masses. Fine scattered punctate calcification are seen bilaterally. There is no suspicious cluster of pleomorphic microcalcification seen. In the bilateral axillary regions, there are few subcentimeter masses, some of which are partially visualized. Bilateral axillary subcentimeter masses, some of which are partially visualied, favoring to represent lymph nodes. This Monday I have to go do another ultrasound and see the breast surgeon. I m kind of freakin out right now. It is possible for them to see something diferent on the ultrasound I m going to do Monday from the one it was done 6 months ago. My mom died of metastatic cancer , so I m really worried right now. Thank you in advance for your information.