I think I'm cheating
What makes you think you are cheating? Do you think it is a good idea?
I heard it's not the best thing to do.
Even though by cheating you may gain something from it, but it is still wrong to cheat. It is unfair to other people and in the long run it is also unfair to yourself too.
Interesting, why is it so?
Deciding to cheat makes it impossible to have a lasting relationship. If you give in to your sudden urge to ruin something you put time into you are not going to be able to build trust with your partner. Not only this, but cheating is something that will really make your partner upset.