Do I need to change??

Why is my dr not offering chromosomal abnormality test, nuchal screen or any blood tests at all? Next US won't be scheduled until 18 or 19 weeks to find out sex of the baby. I'm 12 weeks now. I don't want to wait to see in another month and a half if my baby is not going to be normal. I need to know!! I was super sick I lost 15 pounds in my first trimester. I KNOW I didn't get all the prenatal vitamins in and then I spewed some up too. The first few weeks are the most important to have the vitamins to help combat spina bifida and stuff. My 1st ultrasound was at 9 weeks which was a little too early to tell if there was fluid build up on the baby's neck (nuchal screen between 11-12 weeks). Should I change doctors? Or am I over thinking all of this?