I am on norethindrone, for past 2 week having nasea and missed period, taken 5 pregnant tests- all negative. is this a normal side effect?

Maybe, maybe not: Normally, women don't take 5 pregnancy tests in 2 weeks (once a week works better, because in early pregnancy, it takes a few more days after a negative test for the HCG level to get high enough to show up on a urine pregnancy test). The pills are hormone pills, and can cause nausea or menstrual changes even without pregnancy, too. One should call the prescribing doctor for the next step.