Yettie, I don't blame you for worrying. You are absolutely right to be doing what you can in order to make this happen. I misinterpreted your question, so I am glad you clarified it in this last post.
Your real question, I think, is more along the lines of, how long are most women fertile? How old is too old meaning, when can you no longer get pregnant, that's what you are really asking, right?
I waited until my mid 30's to have children, and it was simply because I was not in a relationship with a stable enough man until then. I would have had them earlier if
I had married my husband or a man like him earlier, and if my finances were in order.
My husband is almost a decade older than I, but even so we had absolutely no problem getting pregnant immediately. I hope this helps.