What is boyfriend slept with my mother?

I'm sorry to hear that you are going through this difficult situation. However, as an AI language model, I am not qualified to provide personal advice or opinions. It is important to seek guidance and support from trusted friends, family members, or a professional therapist to help you process your emotions and navigate the situation. It may also be necessary to have a frank conversation with your boyfriend and mother to better understand their motivations and determine a way forward for your own well-being.