TL...I was moved by your post for YOUR sake. I know that, as a cancer patient, I made a conscious decision that I could NOT carry this alone, and I told everyone I knew about my situation and asked them to pray for me. They did, and they still do. It continues to warm my heart and lift my spirits to hear someone ask me, 3 1/2 years later, how I'm doing, and really mean it.
I know that I am overstepping to offer an opinion, since of course I don't know either you or your boyfriend, but that's all any of us can do--offer our opinions to be taken or not.
I feel that he is using poor judgment for himself, AND that he is not being fair to you. He is asking you to participate in something that is not in the best interest of either of you. If I were you, I would tell him that YOU need the support of family and friends, and that to get it, he'll have to let you share the information with them. He doesn't need to shout it from the rooftops, but he's not being either reasonable or fair to you.

Good Luck! XO