Discolored/bruised nipples?

Michaela • I'm 25, Married, PCOS, Two angle babies, Delivered our twins 7/25/17 at 24 weeks and they are perfect 💙💙

Does anyone else have this issue? Is this a bruise? Or just like a hickey from pumping?? I pump every 2-3 hours for 15-25 mins. (Twins born at 24 weeks in NICU)