Lot of spotting between periods

Hi ! I have a question if anyone can answer me..

In october I changed my birth control. I had been taken pills for almost 10 years and since october I have a copper IUD called Mona Lisa. I think it's a little IUD because I don't have any children yet.

What concerns me is that since I have this IUD, every months, few days after my periods ends I always have 3-4 days with blood spotting. At first I thought it was because my body was adjusted but now that it been few months I wander if it still normal ?