What is the best thing to do on discovering your boyfriend is married?

You ask what to do. well get a brain first there is no excuse to go sleeping around with someone and not know them. You clearly didn't know this person and you start a relationship with him and now that you got your little feelings hurt you are mad and want to upset the world because you jumped into something without looking first. I am sorry but i believe in all taking responsibility for there actions and you are not.