Big hug to you, Emily. I'm sorry you're in so much pain. You've got a lot of support here and we are all sending you love and comfort.
I really think you need to take some time to grieve this loss before you make any decisions about DE. I remember the first time, 3 years ago, that my RE nurse mentioned casually in passing that I might start thinking about an egg donor. I spent the rest of the day crying on the couch, and when my DH got home from work, I wept in his arms, saying "it would be your baby, but not mine." That's not how I feel now, but that's how it felt at the time. The thought of DE was new to me and unthinkable. A few months later I found this article http://www.wellsphere.com/pregnancy-fertility-article/i-used-an-egg-donor-by-suzanne-schlosberg/737024
) and I'd read it over and over again, weeping. Another few months, and I turned a corner and started feeling positively about the idea. And now I'm bursting with excitement about it. I think it's really not good to move forward until you've allowed yourself the time and space to grieve the loss of the genetic connection and truly and deeply warm to the idea of DE. I've heard second-hand stories of women who did DE when they weren't ready yet, and they are not happy stories. And I know several women who just could not get behind the DE idea and chose not to do it, and I respect that. Just tell yourself you're not going to move ahead until you feel ready, and in the meantime keep reading about DE, have your sister get checked, keep gathering information in a casual way, and at some point you'll know what you want to do.
As for your DH, I know that's really hard if you feel you're keeping him from something he really wants, but remember that you're a partnership, and what you want matters, too. And you're not ready yet. It's rare that spouses/partners process this stuff at the same time, at the same pace. It took my DH ages to be OK with the idea. He eventually got there (almost 2 years after me), but now he is totally on board, and I'm glad he was strong and didn't move forward before he was ready. It was hard waiting for him, but what was totally agonizing was that he hid behind his workaholism and was emotionally distant and rarely home. It would have meant the world to me if he stayed "connected" and said "I know you're ready, and I'm sorry this causes you pain, but I'm just not there and I need more time." I would have felt that we were still a team, instead of feeling so alone. So talk to your DH, keep him informed about what you're feeling and thinking. It sounds like he's a good communicator, that's great! If you're having a hard time communicating, let him help you. I read a marriage advice book years ago, and only thing I remember was the principle that "when times get hard, turn toward each other, not away from each other." Isn't that so wise? As a previous poster said, let him in.
I think that, right now, the primary task for you is to take care of YOU. Do whatever you need to do to heal, try to get exercise, gets lots of R&R, do things you love that energize you. All this other stuff can take a back seat for a little while, and then things will unfold from there.
All my best.