Welcome to our forum.
It sounds like J has cut off contact for the time-being. There's not much you can do about that.
Re (from TornAndCofussed, Post #3
"But if I talk to D first, then find out J wants no part of that, I have caused more hurt for D."
In the short term, perhaps. But in the long run, you have established a precedent that you will tell the truth to D, and that he can depend on you to tell the truth. That's worth a great deal in any relationship. Don't be afraid of it. D will appreciate that too, after he gets past the initial "owie" phase.
Just tell D you have feelings for J (if he doesn't already know that). Assure D that you still want to stay with D, 100%. Remember that love is not a limited resource.
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Glad to have you here,