I would say the most important thing you can do right now is to make sure you're getting what you need from your husband. Perhaps love will flourish between your husband and the bf and not you and the bf, but that's no reason you should have to feel abandoned by your husband in any way. RP is correct that vees often seem to be more common and stable than triads and can be very satisfying for all involved even though it may not be what you all envisioned initially. Let us know if you have any questions about the terms being used or if there are any specific problems beyond vague feelings of being left out that we might be able to help you address.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.