Period is always on time sometimes day early or late its 30 days between periods. this time im 6 days late i have the headache and back pain feels like im going to start i havent yet preg test said negative could i still be or what could it be ?

Many things: A pregnancy test will be positive as soon as the first day of your missed period. For accurate testing, the first morning urine should be used. You can repeat the test with a different brand if you want to double check. Other causes of a delayed period include stress, weight loss/gain, thyroid issues, birth control, diabetes, celiac disease, UTI infection. See a Dr if your period is >2 wks late.