Don't ever be scared to lose him sis. Because look at it like this, if he can be so quick to just leave you/the relationship and go be with someone else just like that, then is he really the one? Is this really a good relationship? Does he nourish your soul? I mean you have to wake up. If he repeatedly treats you bad, lies and cheats on you constantly, then he's not the one! What you allow will continue.