Okay i have not had a period since January 13, 2011-January 17, 2011. I have taken 3 home preg. tests and they were negative. I also took the blood test and that too was negative. However I've never missed one period in my life before and now all of a sudden these months have gone by and it's still not here! I am not under stress or any of that, because I know people say you could be under stress and miss it. But i have pregnancy symptoms. I am always tired, cravings ( here and there), headaches, sharp pains in my stomach, nausea, backaches ( lower back), frequent urination, heartburn, constipation, and mood swings!! Please give me your opinions on what this may be!!!