I had implantation bleeding (one day of brown spotting) the day before my period was due. is this a sign that the egg successfully implanted in the uterus and i dont need to worry about ectopic pregnancy? (unless theres a twin, that is.)

It has no meaning: Actually, a positive pregnancy test can tell a woman that prior spotting was actually implantation spotting. It is hard to tell if a woman is pregnant because some of the symptoms seen in early pregnancy can also happen in non-pregnant women. Urine pregnancy test gives a reliable result about 3 weeks after sex (3 weeks after when conception might have been) or 1 week after starting a weird period.