IUD, period?

had sex on the 20th, the condom came off as he pulled off and he came on me. woke up 4/29/18 with super bad cramps(a couple days before period is supposed to start-normal for me) later on i started spotting( old brown blood with clots) May 1st still having the brown blood with clots with some brighter red blood, which is normally what i usually have before the fresh period blood begins. i know with an IUD pregnancy is rare but i’m still worried... since it’s clotty it’s my period right? i got the IUD Feb 7 2018 and i check the strings every now and then and last time i checked them they felt fine.

i’m just putting my hope into the IUD and that the bleeding i’m having now is just it doing its job. my period was due yesterdayish