Next day after sex, bright red but light bleeding 3 days. pregnant? implantation bleeding?

Hard to guess: A positive pregnancy test then tells a woman that prior spotting was actually implantation spotting. It can be hard to tell if a woman is pregnant because some of the symptoms seen in early pregnancy can also happen in non-pregnant women. A urine pregnancy test gives a reliable result about 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after an odd spotty period.