IUD Movement

I've never been able to feel the strings, but every time I've been to the doctor in the last two months since I've had it in it hasn't moved. But I was in a car accident this week and I've had some cramping (I just finished my period so it shouldn't be that). I'm not sure if it's moved, but I don't know if it's urgent enough to go get it checked right away, I have an appointment on the 6th of January. But I also know I'll be seeing my boyfriend over Christmas and we'll probably have sex at some point over his break, but I don't wanna get pregnant. Any recommendations or advice?