Boyfriend wants to fuck other people...

We have been dating for a year and some months and we all ready have had a threesome which was fun and all but couple months pass we dont have sex all the time, yes its probably due to the fact I dont always need sex and stuff but in not having sex like we used to he would constantly bring up him being able to fuck someone else while still loving me and wanting me and I'm the only one he wants he wants to get married to me and build a future with me but he wants to fuck some else, I dont know how I feel about it. The person that he would fuck is the girl we had three some with it's not no stranger. I'm conflicted because I know I'm not giving him what he needs but also I dont want him fucking someone else