It's not fair. And it is also not fair that you can't find support or sympathy irl. We struggled 2+ years to conceive our first, and then got pg "easily" with our second. (But still with ART) and are still working on #3. (8 medicated iui cycles, a successful ivf with a mc at 11 weeks) When we miscarried my bil said "well, you can try again. Sometimes this just happens." Well, yes, but sometimes people don't spend 50% of their income or two years actually getting pg! GGrrr....
With secondary infertility, you also have your other kids to be concerned about. We ended up telling our 5 (then4) year old what we were trying to do, just so he wouldn't worry I was really sick. I mean, he was driving to the 4 or 5 x/week appointments with me for months on end and we didn't want him to imagine the worst. I think the miscarriage was hard on him too. Sometimes he'll talk about our baby growing, and I have to remind him that it stopped growing and died.
I'm not sure about you alisa, but I also feel guilty for wanting this other child so badly, when some people don't even get one (or two). And I feel guilty for spending $$ that could be spent on the kids I already have. Then I feel guilty for not being able to give them another sibling. Can't win!
I guess in 20 years we will have moved onto other issues, but the thought that I will always regret not having another haunts me. And in 20 (heck- in 5) years it will be too late to do anything about it.
I'd love to have some sort of peace to offer you, but I can only commiserate with you.