What Causes Blood Discharge From The Nipples?

Hi. My right nipple would bleed whenever my husband would squeeze it so hard. We noticed this around three months ago but we did not know yet where the bleed came from. Last week, we noticed that it came from the nipples. The characteristic is dark red. I thought that it would just heal but it has been three months already. There are no discharges if my breast and nipple is not squeezed.