I need some advice, ive had the IUD coil in for roughly 6 months my monthly has always been like clockwork but this month i am a week late. Ive been having sickness, sore boobs and fatigue. Ive never been able to feel the strings so cant check. Ive taken a pregnancy test it has shown not pregnant, but i feel how i did with my first pregnancy. Can the copper coil cause false negatives or would there be another reason for my hopefully just overdue period.