Ay sis, mahirap sabihin talaga based sa description lang kasi ang spotting after regla could be maraming reasons, old blood talaga or hormonal fluctuations, pero may chance din ng implantation bleeding kung may possibility of pregnancy sa timing mo, so I'd really suggest checking with your OB to be sure, lalo na kung unusual ito for you. A few of us moms din nag-experience ng ganyan, and one friend swears it was implantation pero nag-PT ulit siya after a week and that's when it showed positive, kaya siguro worth retesting in a few days kung worried ka talaga. Better safe than sorry, alam mo naman!