Sexuality is so many possibilities.. If we stuck to just one, there would be no happy couples. I think you should definately tell your girlfriend about your interest in men. If you keep it to yourself, she will eventually feel your "drifting away" alone with your secret and that will create trust issues in your relationship. If she is "the one", she will try to understand you and even be grateful for your honesty and your trust in her. However, if you prefer dicks and don't like her pussy.. it means she's not "the one".
If you are not opened about it, your "secret" will be revealed anyhow.. be it in your distance, your guilt feeling, your own frustration.. which will ruin your intimate relationship with her.
If you are not opened about it, your "secret" will be revealed anyhow.. be it in your distance, your guilt feeling, your own frustration.. which will ruin your intimate relationship with her.