Need a spark ...

My partner and I have been together for 4 and a half years. We just got engaged two months ago. And moved in together officially last year. When we first met , we weren’t having sex quite yet (a whole year) because we kind of just wanted to take things slow. I’m more of the “get to know you better” type. So after a year I finally gave in and you couldn’t keep us off of each other . It was the best sex if ever had . But then something changed once we moved In together. It was like the sex got old ??? We would start it , cum super fast, and then just go to sleep . It was never interesting or nasty like it used to be.. is there any way I can bring it back? Or should I just leave it how it is?