Hi, thanks for using healthcare magic
In the absence of any protection, then
pregnancy is a possibility.The
blood test for HCG, though , is usually accurate.
If it was taken very early in the pregnancy it is possible that levels may not be detected but in general it can normally be seen by eleven days post conception.
If your period continues to be delayed you can consider repeating either the blood or urine pregnancy test.
Since you recently removed your birth control it is possible that your body has not regularised in terms of your menstrual cycle as yet.
The other causes for delayed period are: physical or emotional
stress, extreme physical activity, inadequate diet, reduced
thyroid hormone, high levels of a hormone called
prolactin, PCOS.
I hope this helps