Well, I've been on both sides. I don't expect most women without children to understand secondary infertility though. And honestly, I feel like I have been attacked a lot on this board for expressing my frustration at not being able to conceive again. I hesitated even to answer your question. But, since I have been through both primary and secondary infertility, I felt that I had a better perspective than most and could answer your question.
I had primary infertility with my first. We were unexplained. I was only 24 and I didn't know of a single person that had ttc longer than than 6 months. I had friends that started ttc when I had been ttc for 10 months. They got pregnant and then delivered a baby before I was even pregnant. It was heartbreaking. I really felt that I was never going to be a mom. It was one of the most devastating times of my life. I really was considering which country I wanted to adopt from.
I finally got pregnant after 4 IUIs with clomid. He's turning 9 next month!
I had 2 spontaneous pregnancies after him.
Then, I decided to ttc #4 (I love kids and babies and just didn't feel done with my family size). Now, I've been diagnosed with secondary infertility.
The feelings are very similar. I don't have the worry of never being pregnant, or nursing a baby, or seeing what a baby would look like that my DH and I had made. Those were fears I had while ltttc #1. I knew that I would get to rock my child to sleep, and send him to school b/c I would have adopted. I know that's not right for everyone, but I would have done it.
But, when you have children and go through infertility, it's still a sad, empty, loss. 1 child cannot replace another. Just like one pet, or even one person cannot replace another. I am thrilled beyond belief with my 3 children (considering I thought I would never have any, that's saying a lot), but it is heartbreaking to go through infertility. It really doesn't matter how many children you have.
I can say that when I try to get support about my inability to conceive a 4th, I hear a lot of "at least you have 3". And while there is a point to that, it still really hurts. I want this baby. I am trying very hard to even get pregnant and nothing is working. I am depressed each month when my period comes. This is very similar if not the same as ltttc #1. I was actually surprised at my feelings, to be honest. I want this baby as much as I wanted my first, and I think that is hard for women without children to understand. A 4th baby is just as much desired as my first. Maybe, if it wasn't so important to me, it wouldn't be as difficult. Maybe each women feels different? I'm not sure. I only know how I feel.
If I don't have another baby, I will grieve. It will be a sense of loss. I will not just walk away. Just like my first.