Do I need to go to an ob/gyn even if im not sexually active?

Yes. Even if not active now you may have been before and as such any exposure to human papilloma virus may have occured. Cancer may develop in patients who may have never had sexual activity. Pelvic exams are routine to evaluate the cervix and pelvis. Also ob/gyn doctors examine the whole patient including breasts and order mammograms. They are in essence the female patients family doctor.
See below. Nearly all the doctors agree that you should go and see your ob/gyn doctor periodically just to be able to get a complete physical exam which is prudent for all of us as we grow older. How often to have a check up is a matter of debate but economics dictate it...Do it if you can affords it, at least every 5-10 years is desirable.
Primary care. Your primary care provider should be able to follow you until the services of an ob-gyn are needed. The current reccomendation for rhe 1st pap smear is at 21.