I have been on the pill for 18 years and recently was switched to Apri which made me gain about 10lbs. so I quit altogether last Feb 14th. I had never heard of an IUD until coming to these boards so I went to my obgyn and asked her about getting a copper IUD and she said that you have to be on your period while getting it inserted. At the time I didn't think anything of it but now I am wondering why? Does anyone know why you have to be on your period?