You describe so well the anguish many women feel over never having been able to have children or who have lost them. My sister still grieves over not being able to have any. She doesn't talk about it a lot. She went through 3 IVF's and several years of trying to adopt. She has three cats and a dog now, and she says they are her children.
It's hard to understand, isn't it, especially when all those women out there have children when they didn't even want any.
Have you considered being a volunteer with children? Maybe even babysitting? Taking on foster children? I know these are not the same as having your own, but they are a way to interact with kids and be special.
You definitely sound depressed. I suggest you consider talking to a counselor. As you say, there are so many things in this world that can be enjoyed, but you aren't enjoying them any more. Life is still valuable and has meaning. Please find a way to get some help, so you can get back to a happy state.
We are here for you, and we care.