What Causes Nipple Discharges From Both Breasts?

Hi. I'm a 27 year old woman. I don't believe I'm pregnant -- OTC tests have come back negative, BUT, I have a clear fluid that comes out of my nipples (both breasts) when I squeeze around the area. I don't remember what made me squeeze originally, but I've noticed this for about three days now. In one duct of one breast, the fluid comes out thick and white. Is this by any means normal for a healthy individual?