Dreaming of an ex boyfriend?

I've been with and know my husband for 4 years, 1 year of marriage. We are VERY HAPPILY married. I'm in my 9th month of pregnancy. Lately I've had multiple dreams of an ex i dated for 4 years in HIGH SCHOOL. It's been 6 years since we dated and about 3 years since I've seen or even talked to the guy! (He would go into where I worked) 
Anywho, I've had very innocent dreams of him. Mostly just friends talking to each other in the dreams. But idk why my brain is even thinking of him lol. He was a HORRIBLE boyfriend. Always cheated on me, I was always crying and upset. I was young and dumb lol. 
Anyone else have this issue?.. It's not like I'm trying to think of the old A hole. 
WHY IS IT HAPPENING!?