What Is Causing My Dizziness, Stomach Cramps And Discharge From Nipples?

I have an IUD and it has been 5 yrs. I havent had it taken out but I have been sexually active with my boyfriend. I am feeling dizzy, lighted-headed likie I am goingto faint an my stomach is crampy. I have a milky discharge coming from my nipples. I have taken 3 preganacy tests and they have all said neg. What could be wrong?