Would I be considered common law if we are together for eight years and have three kids?

To be common law married in Oklahoma you have to have the intent to be married and to hold yourselves out to the public as a married couple. Usually this entails filing taxes jointly, having joint checking accounts, and introducing each other as husband and wife. Your situation is different. You cannot be married at all because your "spouse/boyfriend" is not eligible to marry you because he is still married to another person. If the divorce was never finalized they are still legally married and you cannot marry him and he cannot legally marry any other person.