I am happy that you and your husband talked, but you did not come fully clean with him. I believe that you should tell him everything to keep him informed to make his own decisions with all possible information.
I hope that you two stay happy with you becoming poly and he is comfortable with your choices of people you have relations with.
Also, not all men think that contact is cheating, people can cheat in their minds and hearts, thus guilt is felt. People need to communicate openly and honestly.
But, what do I know; I am new at this too. Good Luck