Hi,
Pregnancy tests tend to be fairly accurate. Either you've used them too early or you're not pregnant. It is normal to continue to have a slight discharge from your nipples even a few years after having had a baby, whether you breastfed or not.
You didn't mention if your period is late. If it is and you are still having the symptoms you've mentioned, I would recommend that you go see a doctor just to be on the safe side.
Good luck!
Rachel Inbar
www.fertilitystories.com