honestly if he's in a common law relationship but pursuing others too, including you, go with your gut. I think you already know that this is not a man to be trusted and is not going to lead to anything good. if he's trying to be more than friends with you now, what makes you think that there is any reason he'll stop if you don't cut off communication with him? Besides would you want to be friends with another person of either gender that you know is basically planning on cheating on? I mean I would have a hard time being friends with someone that is openly doing that even if they weren't trying to make me their partner in adultery.