Antibiotics don't mess with it.
Thanks, I believe your right about the antib. :)
It states that sometimes it stops ovulating, but more often it makes the uterine lining thin to prevent implantation, thickens cervical mucous to prevent sperm from entering the uterus and also inhibits sperm from meeting an egg. I don't believe antibiotics can mess with the IUD since it's in the uterus and not taken by mouth or such. I would call your doctor and check on it to make sure though.