would they see baby at 6 weeks

Could doctors tell that I am pregnant if I had a pelvic ultrasound? I had pelvic pain so I had a pelvic abdominal ultrasound , i last had sex 6 and a half weeks before the ultrasound. 
They didn't mention pregnancy In the report. Would they have seen anything? 
I have still got my period and negative tests. 
They didn't check for hcg in the blood test I had done. I did give a urine sample that they checked and it was negative but I have elevated high white cell count but no infection. 
I don't understand.