Implantation bleeding

So I never had implantation bleeding with my first pregnancy so I'm not sure what to expect. We had sorta put off ttc due to how busy our schedule got last month and this month but between January 1st and February 21st we've had sex 19 times. My period was due sometime around February 19-21(usually comes the 20th) it hasn't come yet but yesterday morning and this morning I'm having extremely light spotting. Could this be implantation bleeding or the start of my period? I took a pregnancy test yesterday before I saw the bleeding and it was negative but also I've been nauseous and really tired. What did you ladies experience before/with implantation bleeding?