Married! Pregnant! Happy! But....

I need some advice. I have been married to a wonderful man for the last 3 years and I am currently almost 5 months pregnant. But I have a problem... no matter how hard I try, I can not get over my ex. He was my first love but I truly believe that he is my soul mate. I didn’t work out because of a situation he was in and by the time he got his sh** together I had already met my future husband. I am no longer friends with him on social media and only see him once in a blue moon but I can help but think about him probably on a weekly basis. I know I love my husband and he is great but I don’t know how to get over this feeling. Any advice would help. Thanks in advance :)