Tell your current g/f that you need some time to think. As the saying goes, separation makes the heart grow fonder, so if she's the one for you, you'll really miss her during your time apart, and this means NO contact, phone, email, or otherwise. Set it for like a week or whatever feels comfortable for you. This could benefit her too, and make sure she's comfortable with it. Don't go out with anyone else during this time, lets not turn this into a small Temptation Island. Keep it clean and faithful. After the time apart, the both of you sit down and have a heart to heart about your feelings, etc. See where it goes. You may discover new things.