Thank you for putting up your problem to Healcare Magic!
Three times negative pregnancy
test almost rules out the pregnancy if they were done at interval of days and not on the same day.
To be doubly sure you should have serum hCG
levels and an Ultrasound
abdomen and consult the Gynecologist.
I think you are not pregnant but you have some problem related to hormonal
Ultrasound abdomen would be very helpful to detect some pelvic pathology.
I hope this information would be both informative and helpful for you.