First time NOT pulling out.

Hey y’all. I finally got my CopperIUD back in. My boyfriend and I are kinda excited to test it out. Yes we been together for over a year. What should I expect? He’s never cum inside anyone like this and I never let me ex do it when I had the iud before . ( I had it put in and then my ex left not long after so I got it took out because it was hurting me ) but my boyfriend now is wanting to try it and I am too. But idk what to expect. Is it warm? Do I feel the push? Will it run right back out ? Please help. Like I said never had this happen. Yes I’m 22 almost 23 and been having sex since 18 but never a not pull out on BC. Also what should I do after ?