Stay or leave ?

So I've been with my "Fiance" for 2 years now . We have a 4 month old together and I have a 1 yr old who he is raising and she calls Dad ... But lately shit has not been the same before he used to show that he cared and fight for our relationship but now its like he dont care ... If i threaten to leave he just doesnt care but back then he used to fight for us to stay together ... Lately hes been having a nasty ass attitude 💯 and im tired of it already 💯 what will u do ? Im just tired but I love him ... Idk