Common law marriage is heavily dependent upon the facts. No one can tell you if you likely have a common law marriage unless they know more facts. In general, however, you have to have acted like you were married. You assert that you didn't do this.
The way you describe it, you don't have just a roommate, perhaps you have a leech! Got news, chikka, it sounds like he's not planning ot move out voluntarily, plus his comments raise questions in my mind whether he might become abusive when you try to break up with him.
Domestic abuse is broadly defined as "a pattern of behavior in any relationship that is used to gain or maintain power and control over an intimate partner." At the moment, he is using a threat in an attempt to gain control over you. For now, he's only threatening with regard to money, but it could escalate to actual physical violence or stalking if he were to become desperate enough. I could be wrong.
If my hunch sounds correct to you, however, you should consult with an expert in domestic violence before planning your strategy about how to leave. This is because leaving is the most dangerous time for a woman. (No amount of appeasing or giving in to threats will work.) A tiger doesn't know he's in a cage until he bumps up against the bars. Everything may be fine, but don't be surprised if more abuse symptoms emerge as you start bumping up against the bars. Because that threatens the nice, comfy life he has here with you to support him.
The phone numbers to call for help are 1-800-799-SAFE (national domestic violence hotline) or 1-843-744-3242 (Charleston).
As a practical matter, immediately get prudent with your finances. Make sure there are no joint credit lines and that you do not leave any credit cards laying around. If he has access to your bank account, open a new account in your name only and quit funding the old one. Then, be prepared to make a clean and swift break, no if's and's or buts, and get into a safe house, if needed. You can replace your furniture. You can't replace your life.
Even though you weren't married and don't have kids, if he stalks you then you may need to see an attorney and get a restraining order, or file police charges. Fortunately, the stalking legislation is on the books and does help to protect women.
For your sake, I hope I'm over-reacting. Too often, however, I see women who are in denial. They say, "It was just verbal" or some other excuse. Abuse is abuse. If that's what it is, call it, be prepared for the worst, and deal with it appropriately. .