confused

I got off the birth control pill(seasonale) 8/13/06 and i bleed a little bit and then i continued to have unprotected sex probably 4 times. My period was then late in september so i took a pregnancy test on wednesday 9/20/06 and it was positive so i took another one on thursday and it was positive both of them were from the same pack the confirm clearly. Then later on thursday i began to cramp and i started to bleed which was like a normal period. So i began to freak out so i went to the doctor on Saturday they tested me twice with very little urine which i had to push out and there was some blood in it. They took it twice and it was negative . They said theirs was 99.9% negative. They told me it was just a period. My period only lasted 3 days shorter than normal. Was mine faulty or could theirs of been wrong. I don’t wont to get my hopes up again. so i haven’t tested again. I am still trying this cycle. so maybe it will happen soon. I just wanted some answers.i am not due this month until around the 18 so if i am late then i will test.