This is a hard one to deal with. I understand what your're saying. On one hand, know that it is wrong to mess with a guy in a realationship, and on the other hand, you do only live once. Being a part of a social circle is not important as long as you still have those friends that you still care about. If these people are true friends, they will give you the chance to explain yourself if you go after this guy and they will not judge you for your actions. Go with your instincts on this one