Brenda,
You posted on this a few days ago and I didn't respond. Frankly, it's because I don't think anyone can give you the kind of reassurance you are wanting, other than your doctor and the medical community.
It would be irresponsible of me to tell you that everything will be fine. And it would also be irresponsible of me to tell you that it won't be fine. There are false positives on some tests, I have known of many cases where a false positive was just that, and I know of a few others where the indicators were there for a reason.
It may also be that an amniocentesis will be necessary to give you the answer you are wanting. My advice would be to really talk with your husband about what life might look like with a special needs child and what your feelings and fears are around this. I didn't get an amnio with my son because I knew that I was-- and could--- love and care for my child no matter what their needs were. And I also know many women who did get an amnio because they knew that they would terminate the pregnancy if the child wasn't 100% 'normal'. In my community, I have known of quite a few families of special needs kids whose parents have beautifully risen to the responsibility. These children have challenges and have also been embraced by our community.
All that to say, it's a very deep, personal choice and even if you do ask this question every day on this site, you will only get the peace you are seeking when you have some answers about *your* particular baby. So, do try to keep that in mind. I also think that if the doctors felt that your pregnancy needed more medical attention, they would certainly make that assertion and have you going in for more frequent ultrasounds. So, try to hang tight, talk with your husband about some 'what if's so you have some idea of what you are both wanting, and go forward ONLY when you have some information about *your* baby. Good luck.