I before have cheated and realise its a shitty thing to do.
It is not worth it. It causes so much heartache and agro.
It makes you a bad person. You will feel guilt in one way or another.

It will increase paranoia/anxiety, and may even cause death (AIDs, or, the girlfriend will chop off your dick)

My advice: Do not cheat. If you so desperately desire to play the field, don't get commited to anyone. If your need to be "loved" by a woman is so great that you need a girlfriend but need to fuck other girls too, see a shrink