I was diagnosed with fibroids in my breast. my left breast is the worst. i had a mammogram, it was normal. my question is what does that mean exactly?

More testing needed.: Fibroadenomas are benign growths in female breasts quite common between the ages of 16 and 50. If they calcify, they can be readily seen on mammograms. If no calcium, they can be difficult to see on younger female mammograms due to surrounding normal milk producing fibroglandular tissue obscuring them. Persistent mass, pain, or risk factors for breast cancer could warrant an MRI exam.

Fibroadenomas?: Do you mean fibroadenomas, or fibrous breast tissue? If fibroadenomas, how were they diagnosed? If you have dense breasts, it is possible for visualization of a fibroadenoma or other lesion to be obscurred by the generalized breast density, so the mammo would look normal.