Since you didn't give your age I can only assume you are in your 20s, and have a higher sex drive, and thus are prone to temptation. If you cannot control yourself (which you illustrated with your ex) then you are not allowed to be committed to your current gf. Until you mature and learn to be committed to one person, you cannot have a commitment. And you must tell the women that you want to date others at the same time as them, then let the girl decide if she is ok with you seeing other people.
As far as telling your gf what happened, you should tell her. You made one mistake, you can repent for it by being honest now, and letting her decide how to proceed. If she breaks up with you, then you have learned that commitment is important to women. At least you should learn that if you play around, you can lose your girlfriend. If you still want to "play the field" just be honest with the girls you date about that. Stop telling them things you cannot deliver. Be realistic with yourself also.
OTOH, if you want to "play the field" you might consider unmarried women in their late 30's or early 40s. They are at their peak of their sex drive, very hungry, their personality is well-developed, they are very mature and have a well-developed sense of self, and are very secure and self-confident. They would love to play with a young guy, but are too shy to ask you, assuming you would not like someone much older than yourself. Personally, they just rock my world.
Last edited by bulrush; 24-07-11 at 12:09 AM.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)