Is it okay to feel this way?

So i’ve been in a relationship with my boyfriend for a year and a half. Things are good, & i’m happy. But lately i’ve been thinking a lot about my ex. We were together 2 years and broke up almost 3 years ago. We have not seen each other or spoken since we broke up and I moved out of state so we don’t run into each other. It’s not like I want him back but I miss our relationship. it really was something out of a movie. I believed (& still sometimes do) that he was my soulmate. I feel guilty even having these feelings since I am in a relationship with someone else. Am I wrong for thinking about my ex? Has anyone else experienced this?