I’m so sorry for your loss. And it is a big loss—don’t let anyone tell you different.
It sounds like you understand on an intellectual level what happened—there was probably something biologically wrong with the fetus and you miscarried, which is nature’s way of saying the pregnancy wasn’t viable. Still, knowing the scientific facts behind a loss doesn’t take the pain out of it at all. And that’s something that few people who have never endured a miscarriage can understand. Your grief is coming from the loss of what you dreamed could be—of expanding your heart to love another child, of watching your boys become big brothers, as well as the loss of all the wonderful things that come along with a baby (joy and laughter, milestones and celebrations). Perhaps you were even looking forward to being pregnant again and feeling a life growing inside of you. So you feel sad. Because you are grieving what could have been.
Also, you are now left with the decision of whether to try to get pregnant again, of whether to go through all that entails—the frustrations, the hormone shots that made you feel terrible, the scheduled sex that may have put a strain on your marriage. So now you need to decide if you are willing to travel down that path again, just when you thought you were done with it. Having to face these choices is something to be sad about.
I find that, in general, most people are well-intentioned. They probably don’t wake up in the morning and think, “How am I going to make someone feel like hell today?” But that’s exactly what they are doing when they tell you to focus on other things. It’s not helpful. That’s because people are generally not comfortable with grief, so supporting someone through it is hard. Their goal is for you to feel better and for them to not feel uncomfortable. Their brains are saying, “I know you are grieving, but can you get over that so I can get back to feeling comfortable?” Try to remember that it comes from a good place. You understand something now that they don’t. It’s hard for people to imagine the complexity of your feelings if they haven’t walked in your shoes.
As far as talking to your children, it depends on their ages. In age-appropriate language, explaining to them that sometimes babies get sick inside of mommy and this baby died is enough. Kids are not as connected to abstract concepts as adults are. They never saw a baby or interacted with a baby, so there is really no baby for them to miss. They will be OK as long as you take care of yourself.
My recommendation to you is to not avoid what you are feeling and accept that you will need a little time. Lower your expectations about “moving on” and follow what your mind and body are telling you. I would suggest talking to other people who HAVE been in your shoes. Reach out to friends and family who have been there. Or try a support group or online forum and connect with others who are happy to share their experiences and listen to yours. In time, these feelings will pass.