Should I be worried about getting pregnant with IUD?

I have had the Kyleena IUD for 17 days. Me and my boyfriend had unprotected sex yesterday. Should I be worried about getting pregnant? I know the IUD is supposed to be 99% effective. I have felt of my strings and everything seems to be fine, I’m just a big worrier. I don’t really feel comfortable asking anyone close to me, so any advice or tips from you would be greatly appreciated.