You have a negative test recently, as in today or yesterday? And you have regular cycles that you can predict, so you are absolutely certain you are 11-12 days late?
It's very, very unlikely - possible, but extremely unlikely - to get a false negative so long after your period is due. More likely you are having a wacky cycle, possibly even from the stress of worrying about it. If you still have a negative 14 days or so after you are due, call the doctor to see about getting a blood test done.
Me (40) DH (47) & furbabies * m/c 7/08 4/12 11/12