Have you talked to your boyfriend about your feelings? Has the topic of poly ever come up between the two of you in the past year?
Personally, I think it is much better to open up to him early on, then years down the road, especially if he is someone you see yourself with for a long time. You never know what his feelings or thoughts on it might be if you don't talk about it, he might actually be interested in the whole idea. Would you be ok with him having someone else, as well?
The characters in another chapter we call life!
T - Wife - hinge in Poly V
J - Husband Poly
F - T's Boyfriend Poly (good friend of J's)