M.P.
You definitely need to see a doctor. I doubt it's a tubal pregnancy because the pregnancy test would be positive. Doesn't matter where the pregnancy attaches, you're still pregnant and the hormones will cause the test to be positive.
My daughter had a tubal pregnancy. She tested positive for pregnancy. She was given chemo to dissolve the pregnancy. Without that, the fetus could continue to grow and rupture the tube.
There are many possibilities for not having a period. Only a doctor can make a diagnosis. Please make an appointment.
And stop being worried and scared. Nearly all the reasons for a lack of periods are not life threatening and can be treated.