Very good advice form robc.
I wanted to advice you to tell him that you want to be a ploygamist now too.
And you like another guy very much.
But I want to add, that I am very pessimistic about your relationship.
Firts of all he scares you with his anger, I would leave him because of that, if nothing else.
Secondly, he persuaded you that he is in love with you, but he actually takes you for granted, being sure that if he feeds you with his talk about love enough, he will keep his hold on you.
You sound to me like you were brainwashed by your boyfriend a lot.
And in your relationship you were always "a giver", you liked him so much from the very beginning, that were ready to put up with his polygamy.