I have an 8 month old, and I developed ropey things in my right breast at the beginning of my pregnancy. Not too long after, I then developed them on the left, along with an armpit lump as well. I have had mine monitored numerous times by ultrasound, always told noncancerous lymph nodes. I am still breastfeeding and still have these things. Breast changes are very common in pregnancy, as you know. I see a breast surgeon because of other breast cancer scares, and she told me I might be feeling these because I'm thin. Anyhoo, she's not too worried but has referred me for a PET/CT scan just in case. If I were you, I would ask for imaging if they persist.