Had ultras for aaa couple weeks ago. came out clear. still hav pulse in stomoch all the time. anxiety going away but worried that ultras didn't find it?

Probably nothing : Very thin patients can often feel their aorta and become concerned that it represents an aneurysm. If the ultrasound showed no aneurysm it's unlikely for them to have missed it. I wouldn't worry at all. And at 19 an aortic aneurysm would be really unlikely unless you had a connective tissue disorder like marfan's or ehlers-danlos syndromes.

Accuracy is high: They can show you the pictures or send to your doc. If good tech and study without a lot of gas in the bowel, it should be accurate. You are probably feeling your normal pulse.