Phoenix

The urge will always be there, it's in our genes. The best way to not cheat is to avoid any possible situation where you may be tempted. Don't go to parties without your gf, don't invite your hot neighbor for dinner at your place, etc.

I don't think your love for your gf correlates to your urge to screw another woman. Just stay away from women, as hard as that may be. Hang out at gay bars or something.