First, he has verbally told you he does not want to be with you. Secondly, he proved this by having any form of a relationship with another person while he is with you. So why are you trying to give him boundaries with another woman. The question is how much do you respect or value yourself? no one can tell you what to do but, follow your heart. Why be second in his life. You deserve better and the best thing is to do just that.
Mystic