I am very sorry about your miscarriage?
How far along were you when you miscarried? Have you had any opportunity to discuss with a doctor.
I'm no doctor, but I'd think that an early miscarriage (less than 10 weeks or so) wouldn't damage your body in any way, so I don't see why it would hurt you physically to try again. You may want to do things like take prenatal vitamins and make sure your lifestyle is as healthy as possible, but, that's about it, physically.
I have a friend who miscarried at less than twelve weeks, and she was pregnant again within a couple of months.... and had a healthy baby girl nine months later. I believe that was baby #5 or #6, too.
If you have repeated miscarriages, you would definitely want to talk to a doctor and see if there's a reason why.
Other than that, though, I'd say that it comes down to what you think you can emotionally stand. Regardless of how long you wait, though, I would think you'd still be very nervous until you get past 12 weeks (or whenever you lost your last baby.)
31 is not at ALL old. Really. You're still in prime fertility years, and will be for some time.