I think it should be normal and yes, week 6 is too early to experience more symptoms. It all depends on one's body. Few experience too many symptoms for few it's easy. For me it was neither easy nor hard. I use to feel a bit of nausea (but never vomited) and tiredness but all started around week 8. Sore breasts is one symptom that usually everyone experience when we conceive. You may wait for 1 or 2 weeks to see more symptoms. But do visit the doctor to start on important medication. Earlier you start better it will be. But it's OK to not experience any symptoms. I have seen few friends who didn't have any symptoms and delivered a healthy child.
Its normal I have no idea i was pregnant until i am in my second trimester