I can relate to so much of this. I had my first child at 23. 14 long years ago.
Until this September, she was my only child, despite years and years of trying to have another.
Something "clicked" finally this year, and I ended up pregnant with twins who were just born in September and are currently both sleeping on my lap.
Secondary infertility is awful and I wouldn't wish it on my worst enemy. I hope you will be granted your much wanted 4th child soon. Good luck!