Letting a guy cum in you

Brianna

So I'm getting an IUD and me and my partner are both STI free and up till I get it we've been using a condom. Since its even safer than a condom I want to let him cum inside me but I don't know what to expect or what to do after. Like how does it feel? Should I run to the bathroom right after? Will it randomly leak out at an inconvenient time?