IUD sex cramps

Lauren
Has anyone else experienced heavy cramping during sex with the IUD? Although, only when he's deep in? I got on the IUD 3 years ago with the same partner and still have this problem. Missionary is fine, it's only cow girl, doggy style etc. when it's deep in.
-It could possibly be that he is rather large (never slept with anyone bigger than 6ish inches and he's 9 1/2)
Please let me know if you think it is because of the IUD or his size