I dont believe it?

SO YESTERDAY MY FIANCE AND I TOOK A TEST AND IT SAID NEG. BUT FOR ABOUT 3 WKS MY HAVE BEEN VERY SENSITIVE (HAVENT CHANGED SOAPS BRAS ECT.) I FEEL NAUSIATED OFTEN HAVENT THROWN UP BUT FEELS LIKE IM GOING TO ANY MIN., I GET TIRED VERY EASILY, I HAVE BEEN EATING ALOT MORE FOOD THAN NORMAL, ALSO RUNNING TO THE BATHROOM ALOT MORE. I HAVE BEEN ON BC FOR 4 YEARS AND AT THE BEGINING OF JULY THEY SWITCHED MY PILLS BECAUSE THEY STOPPED CARRING THE OTHER. IS IT POSSIBLE THAT THE NEW PILLS WERENT EFFECTIVE FOR ME? OR COULD THEY CAUSE ALL THESE SYMPTOMS? ALSO WE BOTH WERE PRETTY SURE THE THE TEST WOULD BE POSITIVE BUT IT WASNT. I HAVE JUST BEEN FEELING DIFFERENT. AND MY FIANCE THOUGHT I WAS PREG. BECAUSE HE SAYS MY HORMONES ARE OUT OF WACK. HE KNOW HOW I AM WHEN I PMS (TO A T) AND ANY OTHER TIME AND APPARENTLY I AM BEING PRETTY CRAZY ( I HAVENT NOTICED) ANYWAY I WAS SUPPOSED TO START ON SAT OR SUN AND HERE IS MON AND NOTHING. I AM LIKE CLOCKWORK ON THIS TOO. HOW LONG SHOULD I WAIT TO RETEST