This could mean that you are subconsciously liking them or hating them. Strong emotions towards something or someone is what usually makes one constantly remembering them. I had this exact same experience. I was thinking about my crush a lot before I finally realized that I liked him. But then on the other hand, I was thinking about this guy who I hated a lot often. He even appeared in my dreams as some really bad guy.
Try to play it slow. Don't say that to the person of who you are dreaming cause they would think that you are obsessed and weird. Just look many times to him/her and when they look you just look away and then you look again after some sec's.
TELL THEM(: Thats what I do(:
Your obsessed. Like when you played a video game for a long time. Soon that is all you think and dream of.