It is not a relapse. That is just the way that the body releases some extra sperm that is in your body so the body can produce a new one. It is a natural and healthy process. More healthy than masturbation in my opinion. After wet dream, a day or two, there is a possibility that you will feel a little different, maybe you can feel like you relapsed or little more angry, depressed... but that is just your mind trying to trick you to get back to PMO.