I had just finished breastfeeding my one-year-old in October 2017, when I felt a lump in my left breast during a shower. I knew there was a history of breast cancer on my dad’s side of the family, but at the time, I was only 36. So, I wasn’t worried. I figured it was just a clogged milk duct.

My OB/GYN insisted that I have a mammogram the next day anyway. That led to a breast biopsy right afterward. When the results came back,...