3 months. I know it doesn’t feel it but you’ve had a really lucky escape. People (myself included) have given years to narcissists. I know it doesn’t make it easier tho. So sorry. 
How did I come to terms with it?
Well, for me it wasn’t all a lie. My emotions/ feelings/ love were real. I had some very happy memories (of course I did, that was how he kept me hooked). My point is I think a lot of people completely rewrite a relationship when they realise they were involved with a narc. It helped me not to. I absolutely identify the low points but I also embrace the happy times and it does make me happy to think of the times I was happy. Those times were real.
I think there is also something in there about forgiveness (eventually). I don’t envy narcs and I would never want to be one. They’re completely empty and very damaged individuals.
Don’t take it personally. It’s not about you. A narc will leave a trail of devastation in their wake. The next person will eventually be discarded too. They won’t change.
Be really kind to yourself. Narcs are master manipulators. People can often get caught up on ‘I can’t believe I let this happen’ and it’s simply not helpful. Build yourself back up, self criticism doesn’t help with that.
Finally, I wouldn’t wish a narc upon my worst enemy. But now I’ve met one and gotten unentangled from them, it’s been a brutal but valuable life lesson. I didn’t realise people like this walked amongst us, now I know - this knowledge and awareness will help me. Not only in dating, but in my career and personal life.
It’s a process. Counselling helps and there are some great podcasts/ YouTube channels out there.
The main thing, is to not get hoovered back in when the narc circles back. And IME they always do.