I just wanted to give you some additional advice. I encourage you both to if possible to let each other know that you are interested in someone else. This can treat a dating relationship more respectfully. Let your girlfriend know you are interested in someone else and decide mutually whether the present relationship will continue. A mutual or individual decision can be made at that time
If you sleep or she sleeps with someone you should discuss whether the present relationship is worth continuing. Discuss your specific options since it may not sit well with the other person. If it does continue, set up ground rules that will respect each other's desires. Make sure that you are truly addressing these concerns
If the relationship is to be ended bow out gracefully and honestly.
That sounds like the road I was going down. Right. I am not trying to sound insensitive just that openness in this situation would be too much information. Just be open not so much that someone gets their feelings hurt. As far as diseases, that is always a possibility because of the world that we live in. Beyond telling each other your intentions the rest is unnecessary