I don't think YABU at all
I think what is unreasonable is that people don't talk about this subject enough, in a supportive way.
I have two wonderful step-children, who I love and adore who live with us. My DP and I have been trying for a year, I have had 6 miscarriages
I have been told I should be grateful I have children in my life - which I very much am grateful for, I love them to pieces, but I also want to add to our family.
If the desire to have a child is there, it's there and it's an awfully lonely thing to go through when it doesn't happen. I don't think it matters if it's a first/second/third or tenth
You have every right to grieve a loss of hope or a loss of a "potential" child when going through miscarriage. You equally can feel the pain and frustration of not being able to get pregnant after having a child.
It's the not getting answers that hurts and confuses, but sadly as I have learnt sometimes you never will understand - but I am as I am told very regularly in the less than 1% who experiences what I'm experiencing
I hope OP that suddenly it happens for you and you get the support you need