Take a few deep breaths, and let it all sink in.
Your boyfriend loves you. You've been together a long while, and you'e about to embark upon a move with him. Maybe what you need is fo him to verbalize his affections more? I know that sometimes I question someone's feelings for me unless they say they love me, and tell me how much I mean to them. If you think that something like this would help you to feel special and valued in your relationship, don't be afraid to ask for it.
Also, this business of not communicating about other relationships needs to stop. He was trying to be conscientious of your feelings, but really, it's a lot easier to start out by dealing with, "Oh, so I met this girl today and she seems cool," than it is to hear "By the way, I've had another girlfriend for the past few months." Communication is the bottom line to making things work, and it's not good for your heart or his to forget that.
It's always hard when you're starting off with poly. We all have pangs of jealousy at the beginning. However, you can get through that because you believe in the philosophy behind poly, and you seem to be self-aware enough to understand your feelings and figure out what all of this means to you. Just hang in there.