Hi everyone. I am not sure if this is normal so I am asking for advice. I am 15 dpo and am having light bleeding occasionally for the last couple of days. I am 1 day late for my period and took a pregnancy test but it was negative. Does implantation happen this late or would it just be my period starting? I am not having usual period symptoms but am having really bad headaches the last 2 days but no cramps. Thanks in advance!