Hi S.,
I had a pregnancy with almost no symptoms after the initial nausea, even into labor. I knew I was pregnant, but I'd had such good nutrition that I remember telling the doctor while I was in labor that I STILL didn't feel pregnant.
Hang in there. I know how scary it can be to wonder how that baby is, especially when it's way to small to be noticed, or to kick or anything. I also had a pregnancy that failed to develop, and it was wierd, because all along I knew something was wrong, and the doctor kept telling me everything was fine, but I KNEW. SO when I started spotting, I knew it was over, and then within 2 days I did miscarry; and frankly, I was relieved, because I was so sure the pregnancy wasn't healthy. Somehow I just knew.
So, for now, do what you need to do. Eat healthy, get the rest you should, and moderate exercise. Do good things for you, and for the baby inside you. No doctor in the world can look in her or his crystal ball and tell you whether you will miscarry or not, they can only tell after the fact. And, hey, don't complain if you aren't sick to your stomach. That's a GOOD THING. (and frankly, my miscarried pregnancy was the one in which I felt the sickest) Those signs or symptoms or their lack may make you wonder, but don't rely on them. Time will tell, and you already know that.
And I side with the doctor on unnecessary tests. Hormone levels probably fluctuate anyway, and if they were decreasing, what good would it do? Even if you were going to miscarry, that, too, would only happen when the body is ready to do so.
For now, you will worry -- there isn't much any of us can say that will take that from you. So keep yourself occupied having fun with your "only child" because he won't be an only child for long. Try to relax about it, and wait and see. It's very hard. It's downright difficult. But worry won't add anything good to your life. Another idea? When you find yourself worrying -- do some floor exercises. They'll be good for you, and a great inducement not to worry in the future cuz they aren't fun ! (ha ha)