HI, thanks for using healthcare magic
Yes, if you have done three tests, up to a month later, then you are not pregnant.
Illness and
stress can cause the period to be delayed.
Other causes are: (a) side effect of medication
(b)high levels of a hormone called prolactin
(c)abnormal levels of the
thyroid hormones
(d)polycystic ovarian syndrome
You may need to consider seeing your doctor to determine if one of these is the cause.
This visit would involve physical examination, blood tests or
ultrasound of the pelvis to take a look at the
uterus and surrounding structures.
I hope this helps