When I was researching copper IUDs, an increased risk of cysts was mentioned as one of the possible side effects. This is especially true for women that are on hormonal birth control that switch to copper IUDs. Basically, the hormones keep you from ovulating, which keeps you from forming cysts in the first place. I think it's more prevalent in women that have recently switched, and I know you've had your IUD for quite some time. It's definitely still possible though.

Do you have any of the other symptoms of endometriosis?

Also, I empathize completely with your pain. Hang in there.