I agree with Jazz...you should go to your doctor. They can do a blood HCG test. Even if you're not pregnant you should get looked at, because there are several things that can cause the symptoms you're describing and only a doctor can diagnose you. Good luck <3
i suggest you go to the doctor for a blood test. with my first child, i tested negative with the over the counter pregnancy test. two weeks later i had an infection that sent me to the doctor. they took a blood test and found that i was pregnant, far enough along that it should have shown up on the store bought test.