Make an appointment and go to your obgyn. And ask for a blood test and that's the most accurate test you can have , sometimes pee sticks don't work 4 everyone you can be part of that % , just go get confirmed and tell them your late, god bless you (:
It sounds like you have lots of pregnancy symptoms. Since you're getting negative test results and you're 6 weeks late I'd schedule an appointment with your doctor to check and make sure nothing else is wrong. Best of luck!