Constant side ache?

Ok, My husband and I are TTC and I'm a week late on my period. I have had some cramping, but I've also had a constant side ache for the past 2 days. You know the kind you get from running? What's what it feels like. It's just on one side as well. Is this a sign of pregnancy? I did take a test yesterday, but it was negative. Can it take a while for a positive test even after a missed period?