Advice please...

Hi everyone. So, my period is 11 days late, I've taken a test before it was due (because of nausea and sickness), which was negative, then 3 days after my period was due I took another one, and again it was negative. Ive just taken another one, and again, negative. But I can't understand where my period is. It's never usually late, and if it is its only by a day or 2. Has anyone else experienced this before? Thanks xx (attached is my most recent test, I keep thinking I see something but I think it's just in my head)