Past sneaking up in Dreams

I had a dream last night, my ex-bf moved to the state I'm currently living in. He got a job at the same company my boyfriend currently works at, and they ended up working together. Without my boyfriend knowing that his new coworker was my ex-boyfriend. It was a really odd dream. And I've had these dreams where my ex just appears out of knowhere. He had a huge negative impact on my life when we were dating and after we broke up. We still talked for a long time after we broke up, sometimes as friends sometimes as more.

I've been in a happy and sucessful relationship for a year and some change now. I have no plans to get back with my ex but the fact that he appears in my dreams more than my current bf is kind of upsetting for me.

Any advice or insight as to why I might be having these dreams? Or ways to deal with them?

I just feel like guilty everytime my ex shows up in my dreams. It's not like I'm cheating on my current relationship but just the fact that my ex pops in my head at all makes me feel like I'm doing something wrong.