Partner worries about effectiveness

So I recently got a IUD inserted, the copper one. My partner is still scared to cum in me... so he pulls out or stops which is such a turn off for both of us, when I had it inserted I was in pain for like a week and a few days.. He thinks it might be inserted incorrectly but the X-ray and ultrasound is clear. And the pain is gone... Also is it possible for him to feel the IUD inside me while having sex? He said the bottom part of it hurt him or scratched him? How can I reassure him that the IUD is super safe and super effective?