Ang implantation bleeding ay possible talaga, lalo na kung 3 PT na positive mo, congrats, mama! But para sure, I'd really suggest follow-up ultrasound in a week or two para makita na talaga, at kung may other concerns ka with the bleeding (like sobrang dami or cramping), best to call your OB right away kasi sila lang ang makakasiguro ng details. A few of us moms dito went through the same worried stage, so totally get it, the waiting game is nerve-wracking!