How long should I have waited?

I had unprotected sex with my boyfriend 6 days after I got the IUD implanted. I got the iud on the first day of my period and PlannedParenthood website says if inserted within seven days of your menstral cycle it will be effective immediately, other sites say wait a week to two weeks! which is right and should I be concerned? I also just started having spotting yesterday and my period ended a few days ago.