Pregnant but no symptoms - should I worry?

Found out I am pregnant at 3 wks 6 days. I am now 4 wks 2 days. To be honest I took a test for the sake of taking it not because I had any symptoms but should I be worried? The only discomfort I have is some middle back pain but that was there before conception. I also find myself short of breath sooner than usual. Nausea or fatigue has not made its way to me but now I'm freaking out I could be having a chemical. I have no clue! Is this normal? 
I'm usually really sensitive. I get motion sickness in anything that moves!