It could be a number of things. As before mentioned, if you are very low body weight you can miss your period. I've missed it here and there when under massive amounts of stress, but not like you've described.

I get the fear of going to the doctor. Especially when things like speculums and stirrups are involved. If nothing else you could call ahead and let them know that while you want to talk to a doctor about this concerns, but are refusing a pelvic exam. They may say they can't help you without the exam, but a good doctor would still talk to you about possible things that could be wrong or could do blood tests for hormone levels, etc., if they feel that would be appropriate. Just remember when you go into that office that you have the right to refuse care. If they insist you have that exam and you don't want to, let them know you have your rights and ethically they can not force you.

I would start with trying to find a good doctor who will respect your wishes. While it's true they may be unable to help you, they can still talk out your concerns and if you feel comfortable enough with them, perhaps you'll be able to drop your drawer and spread 'em. (I use humor and vulgarity to conquer my own fears of such things).

Also request a doctor of the gender you feel most comfortable with. Myself I've only had one man do a pelvic exam on me and regretted it. I insist on a woman and when I was offered up a man when my doc was unable to make it, I refused and rescheduled my appt. I know my sister feel uncomfortable with a woman doing the exam. To each his own, just know what would make you feel more comfortable and request that gender just in case you decide to go through with it.

Good luck, I hope it goes well for you.