Bleeding with IUD ?

I’ve had the Mirena for almost nine months. I still have a “period” every month but I bleed almost every time after sex. Both my mom and my aunt have the same IUD and neither of them gets a period of bleeds after sex my aunt did mention she had to get her strings cut. I just wanted to know if any of you ladies have had anything similar happen ?

P.S I can feel my strings it feel like they go upward.