It could be that something in recent days triggered a memory of the person. Alternatively, the "cheating" might symbolize some behavior that you thought you had left in the past. For example, if you recently began smoking after years of being tobacco-free, your dream might illustrate this as cheating with an old flame.
It depends on what you are thinking about him. Sometimes there will be nightmares, sometimes there are bad dreams which comes because of bad or negative thinking or doubt on him.
This only means that the guy probably is someone the dreamer sees regularly. The dream expresses the dreamer's jealousy and lack of trust. It reveals no reliable information about the girlfriend or the other guy.
he is cheating on you
The dream suggests the dreamer has a jealousy issue. It is also possible that the dream might be pointing out indications of cheating that the dreamer has ignored in real life. However, the dream is about the dreamer; it provides no information about "the guy" that the dreamer does not already know.
If she refers to you as the guy on the side it means she is cheating on her boyfriend with you
The dream reflects your own attraction to this guy, or your interest in guys in general. Your dream only expresses your own thoughts and feelings; it does not mean that the guy (or any guy) is thinking or dreaming about you.
Your constantly thinking about this guy.
It means that guy friend was thinking about you at night..
The dream expresses the dreamer's emotions in some way. It provides no information about the guy.
The dream could express remaining emotional ties with the guy.
It means you like him/her.
then he must be cheating on you if he has a girlfriend? i mean if he likes you and has a gf then he must be cheating and wanting you?