Well my advice, I would go see a medium. If you were closer I could recommend someone...my Aunt...she's AMAZING. I know your atheist, but cleanse the room first and the rest of your house for sure. It may help relieve why this spirit is haunting u. I would love to see your paintings. The pics may give you more answers to what and why. Hope it helps. I personally would cleanse and pray, but we all are different and have our own beliefs.