I have not had a period for 3 months. i have had 3 negative pregnancy test, no changes to my routine or stress levels. could i be pregnant? i dont know what is going on?

Delayed ovulation will cause delayed menstrual events. There are multiple potential causes , including polycystic ovarian disease (PCOD), and sources of stress ( heavy exercise, emotional, job or school related). See your gyn provider for an exam and other testing, and ask about low dose oral bcp's to stop constant estrogen stimulation of endometrial tissue.