Why do I dream of someone I once was in love with?

I barely think about this person throughout the day. I was completely in love with him(Jeremy) l lost him 5 months ago.I went into major depression. I wouldn’t go out or talk to anybody. I ate every 2–3 days and wouldn’t sleep for hours because I’d cry for him. I still love him, but I eventually dated two other guys after him trying to get over him, which I did. Those guys both left me for some other girl, and everyday for a month that that happens I dream of jeremy wanting to be with me again and it feels so real like when he kisses me in my dreams it feels so real. Today, I woke up having a dream about him for the first time in a month. He kissed me and i felt all the stress just being ripped outta me. I woke up feeling stress free. I don’t know if anyof that has to do with being stress free in the morning but I’ve been so stressed lately.