Had sex when app said I was at my highest chance of conception

Emily

Had a missed miscarriage at 6 weeks in December. This is my second period to start if I don’t get pregnant. I should start Sunday, each test I’ve taken has been negative. With my daughter I didn’t get a positive until the day I was supposed to get my period. I noticed very light pink spotting today just a bit ago. Like is it an early period or implantation bleeding?