My period started on time but super light, just wearing a liner. it is red and brown, and has stayed light for 3 days now, barely filling the liner. i am freaking out.. no symptoms of pregnancy such as nausea or mood swings, but is it implantation?

A person can't tell: Wait. A positive pregnancy test can tell a woman that prior spotting was actually implantation spotting. It can be hard to tell if a woman is pregnant because some 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 been), or 1 week after starting a "weird" period.