As a humanist, I have no faith that nature knows what she's doing or that any god has any perfect plan. Men can procreate long past the age when their sperm are likely to be defective, and women become fertile years before they have the wisdom to be good mothers. Nature's law, AKA the law of the jungle, would leave us all behind when we start getting old.
But human experience knows we can continue to appreciate in value even as we pass our physical prime, and that the latter may not end as soon as younger folks assume.
Some women have babies. Some write books. Some lead nations. It's unfortunate--and unsurprising--that patriarchal culture is too scared of all of them to value any of them properly.
Your hormones are nobody's business but your own. You have nothing to prove to anyone that matters. Be yourself.