Can a man change?

I’ve been dating a guy for almost 4 years now and he’s a totally different person now than he was in our first year together. I don’t know what changed, but now he’s very cold and aggressive at times. He comes off as he thinks he’s better than everyone else. I never got narcissistic or manipulative vibes from him in that first year but now that’s what it seems to be. Im not sure if I’m in denial or just very ignorant to it all, but can a man grow into being a narcissist or is that something they always are, they just don’t always display it? And could he ever go back to the way he used to be?