Last period: Dec. 26. Next expected period: Jan 26-27, today is Jan. 30th. The last 2 days I have filled up (estimation) of about 1/3 of a light sized tampon with blood. I have had what feels like period cramps. I am a super sized tampon girl with my periods, so this is out of the normal for me, which is why I don't think it's my period. Could it be implantation bleeding? I have taken 3 HPT's and all have came out negative.