As sambob says, there are temptations everywhere, i have been married 20 years, and i stil look at women that are attractive and think cooorrrrr shes nice, but i would not act on it, my wife will see a man shes thinks is wow, but i know she wouldnt act on it. the thing that would be bugging me is could you trust them both if they were alone? i think maybe you could because they know your aware of things. i dont think he should have txt'd her with his thoughts. 7 years is a long time to be engaged to someone and you cant throw it away lightly, talk to ya b/f tell him how you feel, he should have had the nuts to be honest from the start but as you say nothing actually happened. one thing i have learned in 20 years of marraige is that its best to be open and honest from day one, ok it might make things a bit awkward for a while, but life is to short and you only get one
i hope you can sort this. take care x