If your partner starts getting emotionally attached to someone else, just like any relationship, then it is their responsibility to end the relationship with you. It isn't any different. Do you think that being in a completely monogamous relationship is going to change that? Because it doesn't. And as far as diseases are concerned, again, always use protection and get tested regularly. Once again, whether in a relationship or not, all it takes is one time to catch something, so an open relationship will not make a difference. Considering I am 26 years old and have never even had HPV, unlike most women my age or younger, I know that using protection is the way to go. So does the boyfriend. But it is still your responsibility as an adult to get tested regularly anyways. It also helps prevent illegitimate children. Or, on a personal note, they could do like us and not mess with anyone who doesn't like anal. That always takes the risk out of getting pregnant/getting someone pregnant. Just sayin.