It sounds like after 18 months, this relationship is dead in the water. Begging and arguing, ironically, will just prove his point that the two of you are not on the same page and one of you is trying to convince the other of their righteousness.
I’m sorry you’re heartbroken. 🙁 Break ups hurt, but if you focus your energy on yourself, you have a better chance of healing better and more quickly. It’s okay to feel badly for yourself, but I want you to be active and start a new exercise routine, join a new gym, spend time going out often with your friends and family and others who are supportive of you being healthy, strong, and healing.
Volunteer with people and groups less fortunate than yourself and/or political or business groups that you think may make the world and yourself better. If you take the focus off of the failed relationship and start putting it on positive endeavors, you’ll realize there is more to life than your sore heart.
I know you’ll feel better in a while. Hang in there. 🙂