How could I know if the lumps are just fibricystic breast changes or something more serious like breast cancer?
You cannot. A lump needs to be evaluated. See your doctor.
See your doctor. I have been a breast cancer surgeon for almost 20 years and I am still fooled by some exams. With that said, there are some generalizations about which breast lumps are more concerning than others. Cancers tend to be rock-hard, fixed, and 3-dimensionally round or oval. Benign lumps tend to be rubbery, cigar-shaped or pancake-shaped.