I can go months even a year with out a period my mother was ver irregular before her first child my physician is worried but my gyno has run tests and everything is normal other then the lack of period?

Absent period ?'s: At seventeen, severe stress (emotional, school, work or heavy exercise) can cause failure to ovulate. Not having menstrual function is certainly not "normal" at seventeen. Tests done should include a pelvic ultrasound, FSH/LH and prolactin levels. Consult your gyn physician to see if these tests are all normal, and if so, get a consultation from endocrinology to determine cause.