What Causes No Period, Constant Hunger, Abdominal Tightness While On Birth Control?

I am on birth control but other than that I don't use any protection for sex. I've missed my period two months in a row and am having headaches, lower back pain, constant hunger, and tightness in my lower abdomen. I took a pregnancy test that came back negative, and I am going to wait a week and try again. But my main question is am I having pregnancy symptoms or am I making myself think I am? and should I stay off my birth control until I find out?