It is common for some amount of white discharge to be seen throughout a menstrual cycle and the consistency and the amount varies depending on the hormone status. The presence of an IUD is perhaps leading to the excessive discharge owing to some irritation. Yet, since the discharge is seen increasing of late, I would ask you to get a clinical evaluation by a specialist to exclude vaginitis
, erosions and/or polyps and if deemed necessary, replace the IUD. A trans-vaginal sonogram is also needed to see the condition of the pelvic organs; pelvic inflammation also should be excluded. Hope this helps.