What Causes Stoppage In Periods?

I have a real bad headache, am always tired, have incredibly bad cramps, and have not had a period in over a year, and I am still a virgin so I cannot be pregnant. What could this possibly be? I also get sick off and on, a queasiness in my stomach. I am eighteen years old. I went to my GYN and she had to take me off of birth control because of high blood pressure, and I have no insurance since I just graduated so I cannot go back to her. I have polycystic ovaries, and a thyroid disease.