Human woman/ alien

[Littledear51]

Series of books read about 12 to 15 years ago. Woman in present time works for the US government with a man that she loves. She has a son and a home in Colorado. She is an alien posing as a human. Originally came to earth with a male partner that died portraying himself as King Arthur. They have a hidden spaceship and wear a medallion that stores their conscience, when they age they regenerate a new body on their ship.
They are fighting aliens that destroyed their world and trying to prevent them from destroying earth. The books bounce around and include area 51, Easter Island, Stonehenge.