Pregnancy symptoms do NOT mean you are definitely pregnant. I had "pregnancy symptoms" before I for pregnant and had none when I actually got pregnant.
In nearly all cases if a doctor says no, you're not pregnant.
I would think the Dr did the right test to determine pregnancy. I had a friend w/ the same issue & was pregnant. I believe she had a urine & no blood test done.
Did they draw blood?? Chances are if the drs said no...then you most likely not. I was 3 weeks when i found out via urine...so even if you were early im sure your drs would have picked it up. I had my first OB appt at 4w2d and she could feel that i was preggo when she palpatated my uterus...it was already distended or firm...