I don't like the tone that your husband has taken, that YOU need to learn more on polyamory. This is not an illness. One party doesn't just get to do as he pleases and disregard the needs of his parnter just because he is poly. You both need to learn together, including learning how to communicate your fear and insecurities to each other. It sounds to me like poly made visible some holes in your marriage that need to be fixed. Part of the process is learning to communicate together and be responsive to each others needs.
It could have been too much too fast. Have you been doing spontaneous things together lately? Have you been DATING each other? Do you have hobbies that don't involve your husband?