missed period on IUD

Ashley
Hey girls, 
I got the Skyla IUD the end of April. I've had a period every month since. Well this month, my 7th month with Skyla, I've missed my period by almost two weeks. I usually have symptoms of cramping a week before all the prior months before with my Skyla. I've had no cramping this month. Is this common, or should I test? If I test and it's ectopic, would it even show up on a pregnancy test