Mazal tov on your wedding!
Thank you for reaching out to us.
Extended spotting such as you describe can be tricky to navigate. At the same time, while spotting is very common during the first months of using a hormonal IUD, it often abates. Some women on this type of contraceptive can go years without becoming niddah. There can also be spotting after removing a hormonal IUD as the body readjusts.
These are all factors to weigh with your physician before making your decision about whether to remove the IUD. You can learn more about this, and about other types of contraceptives, in the Family Planning section of our site, starting with our page on choosing a method. We discuss the IUD and IUD removal here.
Halachically, not all spotting makes a woman niddah, requires her to delay starting her clean days, or invalidates her clean days. For example, a light brown with no hint of a reddish tint (e.g., the color of coffee with milk or lighter) is not a niddah color and is fully acceptable even on a hefsek taharah. It sounds as though much of the spotting that you have been experiencing meets this description.
Learn more about the laws of stains, when they make a woman niddah or disrupt the clean days and how to prevent becoming niddah unnecessarily on our site, on our pages on stains and toilet paper.
Please let us know if we can be of further assistance.