Why does he do this?

Okay so when we first started having sex he would always pull out. But then, we went to a party and got kinda messed up, and he accidentally came in me. And then he just did it again. And again. And again. And I love it. The problem is, my Nuva ring fell out of my vagina and I have no clue where it went or how long it's been out.. so.. I'm going I get on birth control after I rule out pregnancy, but I'm just wondering why he started cumming in me? He would always pull out.. until that one one he did.. and now he just refuses to pull out.