Please help!!!

My boyfriend has been on this split roasting kick. You would think like I would like two guys but I don’t like talking about it or thinking about it! It makes super upset!! I have told him over and over this week that it upsets me but doesn’t stop talking about it! I don’t know what to do! He says he doesn’t think he would want to do it in real life. ( we have a long distance relationship going on during the week) I just don’t know what to do and why it upset me sooo much he literally just wants to talk about it and talk about it during “fun time”. Please help!!!