IUD in place....Should he finish inside?

Okay so I got an IUD (Skyla) placed in September of this year and I haven't had any issues with it other than the occasional unbearable cramps. I have noticed that since it was placed my periods have begun to be lighter and lighter to the point where my boyfriend and I sometimes panic about being pregnant. I definitely should be taking regular pregnancy test just to make sure.

My dilemma is whether or not to let my boyfriend cum inside. We don't use a condom the whole time we have sex. He now usually puts it on before he feels like he's about to finish, but we both want to try it without a condom.

My question to you ladies that let your partner finish inside is how does it feel? Have you ever had a scare? How reliable is Skyla? How hard is the clean up?