A little confused

Basically I was due my period on the 8th of November and now it's 11days late no sign of it I've done 3 pregnancy tests all neg on the 1st of November (tmi) when I went to the loo I found a tiny amount of blood in my CM and again Sunday and then nothing at all. My sister told me about her friend that when she took hpt they would come back neg unless she went to the doctors for a blood test. Would just like some advice please. I'm a mum of one already would like to pregnant again but we're not trying or preventing thank you