Why is he doing this?

ok so me and my ex bf were together for 4 years and lived together for 3in a half i have my own house so we rented out the other rooms to people that we know. A friend of mine and a friend of my bf at the time well me and my bf broke up and one night me and my exs friend got together and been hooking up ever since! well hes always saying hes ready to settle down and i explained i was to all i do is work come home clean and cook he goes out works and yea he is really cuddly some days and others hes always like ur not ready for a serious relashionship i go are u just aying this cause u dont want me beacuse im ur friends ex or what n he said no it has nothing to deal with that.... we sleep together almost ever night till he starts this which is like every other month helppppp y does he do this