AF 6 days late

I've been driving myself crazy testing every day since the day before I was supposed to start AF and all I've been getting is BFN! I got a positive with my daughter at 3 weeks preggers.... I've been super tired dizzy and had very slight cramping( had with my daughter and my 3 miscarriages) not like period cramps because they come and go. I feel like if I am pregnant it would show already. I took a digital opk and it peaked on2/4 so I know I ovulated... What's going on?! Any advice???