Common Law Marriage
If you never had a wedding ceremony or obtained a marriage license, you still might be married. Common law marriage is a situation in which you and your partner are considered married under the law because you hold yourselves out as married by your words or conduct. Colorado is one of the few states that still has common law marriage.
More often than not, only one person considers themselves married and the other person disagrees. If this situation occurs, you need to have a contested hearing in which the judge resolves the factual issue of whether you were married. The judge will rely on documentary evidence (i.e. holiday cards, emails, texts), testimony from friends and family, titling of property, and the handling of finances between the property, etc, to determine whether you are in fact married.