I have been with my boyfriend for 12 years. We bought this house together although only his name is on it. I was divorced and he said he could get a better credit score if we weren't married. 12 years later we still are not married and I want to leave. I have paid half of all of the mortgage payments, I don't believe that we are considered legally common law married. Do I have any legal rights at all to the house? Or am I just simply stupid and out of luck? We live in Colorado if that makes any difference.

This site indicates what might qualify you as a common law marriage:
Colorado Common Law Marriage | Colorado Divorce & Family Law Guide

However, if the house was purchased before you started to cohabitate, it might not be considered marital property and not be subject to an equitable distribution:
Colorado Divorce Laws - Colorado State Divorce Laws

There is no way we can give you a definitive answer here because there are too many factors and CO law is not very specific on these points. You need to consult a local divorce attorney to determine whether you can claim a common law marriage and/or claim a part of the house.