What Causes Nipple Discharge And Itching On The Breast?

When I got up this morning there was an oily ring on my bra, shirt, and even my sheets that had come from my right breast. I have attemped to squeeze the nipple to examine any discarge but nothing came out. That breast was also itching yesterday. I have a son that is 5 months old and I'm wondering if the discharge could be from the changes my breasts are still going through or if something could be wrong.