My story is a lot like your story with your ex except I married mine and after 5 years of lies, Empty promises, cheating, job loss etc.. I'm thankfully now divorced from him..
Perhaps you should take a break from any kind of romantic relationships for a while and concentrate on the one the truly matters YOURSELF.. Start reading up on codependency.. Codependent No more by Melody Beattie and Women who love too much by Robin Norewood are two very good ones to get you started..
You will be an RN in a few short months, please please be thankful that you are no longer in a relationship with this man.. Imagine being with him if he ever got arrested for drugs.. Your career that I know you've worked so hard for would be ruined in an instant..
The best way to get over this guy is to go No Contact.. As long as you keep him in your back pocket he is going to keep coming around.. He's not coming around because he loves you, he's coming around because you are a potential enabler.. Please respect yourself and the new guy you are with because its not really fair I him that you are still communicating with your ex and block and walk...