Why did the two of you break up?
Why are you trying to find him?
What will you do if you find out he's in a relationship or married?
How old are you now?
What if he's not the same as he was back then?
Your dream is simply an extension of what you want in your waking life. When you think about your high school love, you remember how great he was, how well you got along, how he treated you and how you felt back then. Now that you are older and may have been through your share of heartbreak, that relationship looks even better than ever.
It's not uncommon for our conscious desires to make their way into our unconsciousness and into our dreams. There's nothing wrong with enjoying these dreams as long as we realize that real life may not live up to the dream. So if follow these dreams in real life we have to remember that we do not know what we will find after all this time, and if we find something we don't like, we have to figure out how to accept it, after all, we've changed too.
I welcome your thoughts, let me know if you want to talk more