I have been on both sides of the "Where's My Period!?!!?" fence :)
If you have not been (which you probably have not yet) I would go to the doctor and get a pap smear. A bacteria infection could be the cause of a stalled period (it has happened to me twice).
I do not recall ever having a positive urine test early in my pregnancy (and I have 4 beautiful little girls) :) My level are always so low. In my opinion your best bet is going to the OB and having them test your blood for pregnancy.