white discharge, no period...HELP?

Okay so ever since I got my Mirena IUD 6 months ago I have had dark brown discharge everyday. (I know that's normal I even spoke with my gyno about it.) My periods have been somewhat irregular since I got my IUD but still pretty consistent. The beginning of this week when I was supposed to start my period the brown discharge stopped BUT now I have milky white discharge and I still have not started my period. Nothing else is bothering me, no pain, no signs of infection, etc. I am a virgin, my boyfriend and I just do hand and oral stuff. Any ideas as to what could be going on? Thank You!