baby has goopy/crusty eye - what can I do?

Jg • Pregnant with TWINS after mc in April 2015 -looking forward to this journey - trying my best not to be anxious
Hey everyone I'm hoping I can get some tips on how to help my little guys. I have 12 week old twins and both seem to get very crusty and goopy eyes all throughout the day - we've been to the dr and they've swabbed them and it's not an infection - I use warm cotton balls constantly every day to wipe their eyes as well as put some breastmilk around their eyes (a nurse told me it's good to ward off infection) however what could this be and how can help make it not do this