Really confusing?? Help

Okay so I went to the ER tonight for cramping. They took blood, urine, and ultrasounds from me. They came back and said All my blood test were perfect but my urine had white blood counts? They said my cramping probably resulted from a UTI. But they did ultrasounds just to be safe. On the regular stomach one she couldn't detect anything. But on the internal one we saw our baby. My question is, she played a heartbeat out loud but I didn't ask if it were mine or the babies (the lady was very rude so I didn't want to ask her more questions) if it wasn't the babies heartbeat is it normal to be 6 weeks without hearing it and have good blood work? Thanks everyone just really nervous about something going wrong.