Questions about sex on Mirena?

I wanted to get Mirena because I have heavy periods and for protection against pregnancy. I got it in today and it hurt bad but now it's just cramps. I've been with the same guy for six years and we like to have pretty vigorous sex, and now I'm worried that something bad could happen because of it. It could just be my anxiety, but I want to know what other people think. I read that even the strings can get pushed up inside you and you'll have to have it removed surgically. I want to know if I made the right decision or if I should get it removed. I don't want it to affect intimacy with my boyfriend.