I'm so sorry!! I know EXACTLY what you are going through! When I had my first ultra sound, they said my baby boy had a chordid plexis cyst. I was TERRIFIED!! They told me it was a normal kind of thing, and although it doesn't happen all that often, almost all of them go away. He didn't have any of the other markers for Downs or any of the other chormzonal (sp??) abnormalities, but I was still so scared. About 6 weeks later, I had the follow up ultra sound, and it had resolved itself... but those six weeks we AWFUL! I looked at all the web sites I could, and basically ended up scaring myself to death. I cried myself to sleep, almost on a nightly basis... and I was no fun for my (than) 2 year old son.
Now, Dex is 3 months old, and healthy as can be! He's super happy, and super mellow! He's been sleeping through the night since he was born... I'm truly blessed, and you are too!! Just remember, the numbers are in your favor for everything to be fine. And... of corse you should be having kids! That was the first thing I thought when they found that cyst, too. I've had 3 miscarriages, and I had that "stinkin thinkin".
Please let up know how it works out, and our prayers are with you!