In my opinion, no this is not a relapse. Most people do not have control over what they dream about and the body's natural reactions to those dreams. However, you do want to keep your mind occupied with non-sexual thoughts during your waking hours as much as possible so your mind doesn't have as much to fantasize about.
I am just saying, focus your thoughts and attention on sports, reading good books, friendships, etc. and don't feed your mind lots of fantasies about girls and sex. Put non-sexual thoughts into your mind when you are awake so you don't dream as much about sexual things when you are asleep.
