This is just an unfortunate side effect from having the IUD. I had the Mirena IUD and bled heavy for 3 months after insertion, then spotted nearly the rest of the time and had a handful of other extreme issues. I had my IUD removed about 6 months after having it inserted due to the side effects. It's well known that with any long-term birth control that you have a higher chance of spotting versus being on the pill. You shouldn't need to visit your doctor unless you feel that the string has come down your vagina, or start feeling a sharp pain, as both of these issues can be caused by a repositioned IUD.
Thanks for your quick response. I will wait for the time being and observe. If at all there is acute pain or heavy flow i will visit my doctor immediately. Thanks again and will keep you posted.