Worried what do yall think?

So I have an iud and havent been able to find my string for a while. I dont get my period because my iud. So about a week ago my bf came in me and the plan was to get plan b just to be safe but when we got there the pharmacy was out of the brand my insurance covers and we were both broke so decided to trust the iud. Well this past weekend i had light bleed spotting and some cramps but then it went away after two days. I know peoplewho have gotten pregnant with an iud. Should i be worried that was implantation bleeding.