All joking and sneering aside... my suggestion to you would be self-control. If you constantly jump from one relationship to another with the 'grass is always greener' mentality... you will never be happy with anyone you find.
Take some time to reevaluate the choices you have made and compare those with what you really want out of life --- what you really want out of a relationship.
You're hurting yourself in the long run and creating havoc for those you encounter (trust issues for the girls you cheat on.. for one), and this is all really unnecessary --- even cruel. Assume responsibility for your actions. It's the only way you'll ever be truly happy... and it will minimize the hurt you inflict on others as well.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen