Iud lactating and late

I had a baby June of 2014, she and I have an open adoption with a lovely family meaning never once did I breastfeed. I had my mirena placed 6 weeks after when they allow it I remember it was sometime in August of 2014 was fine for awhile started to have abnormal bleeding and it's been looked at a million times but I'm starting to lactate off and on for long periods of time I have no other children and it's driving me crazy all the doctors I've seen are stumped. Any ideas?