Thirty six is fine, K.. I had my son when I was 2 months shy of 41. Not by choice; we'd been trying for years, gave up, then surprise! :o). He is healthy, keeps me young and gives us joy every day.
A word about "going back to the well" for another child: yes, having a child is a risk -- at 22 or 40. If you are worried, you need to decide up front what you would do if you found out something was wrong. And there are so many false positives with the CVS test, that it's hard to rely on that one.
If you feel like you are incomplete without another child, then by all means, try. If it's meant to be, it will be. If not, then ask yourself the hard questions so many have already posted. Ask yourself how life would change? Would you resent the child for changing your life -- or blame yourself for changing your family's life?
Another child will change your family -- consider all the possibilities and do what's in your heart. Good luck!