indeterminate pulmonary nodule....help!

[gqmom]

On my initial CT scan during staging, a pulmonary nodule was identified measuring 4mm (in May 2011). On subsequent CT scans, the same nodule was seen and was 3mm. My oncologist says this was most likely because the scans were done at different locations, different scanners, etc. On the last CT, the report says that the nodule "appears to be less dense and less well-defined" than on the original CT scan done in May. This scan was in December. My oncologist is not concerned and feels that it is scar tissue...not metastatic disease. I went to a pulmonologist and she says that she can't be "SURE" without a biopsy (which can't be done because it's so small) but that it could very well be scar tissue. She also checked with her colleagues and they agree. They have all said we will watch it with CT scans every few months. I'm so scared it's cancer....I can't stop thinking about it. I'm wondering if anyone else has had something like this and if it was NOT cancer. I am stage 2A (T1aN1miM0). ER-/PR-HER2+; left mx, 4AC/12Taxol and Herceptin; now Herceptin every 3 weeks.