Time heals all wounds, though the waiting is insanely difficult. I'm awful at that part. Lol
It sounds like he may have been cheating on you. That's pretty quick to move on in such a way that's they're looking at houses together.
I think you did the right thing and you shouldn't question your decision. You knew in your heart something wasn't right and you made sure you weren't stuck with that mistake.
Maybe he loved you in his own way, which may not be the type of love you would give or expect to receive. If he truly is a narcissist, their "love" is more to do with loving what they get from being with you.

Just keep busy, surround yourself with loved ones and remember that you deserve better and you did the right thing.