My last period was on june 24 2010. My boyfriend and I had unprotected sex on july 4th and 5th. He released sperm inside of me on both days. A few days later I've been having stomach cramps and head aches. My period was due to come on the july 22 but it havent came yet. I been have head aches and cramps but no blood almost everyday now. I went to the doctor on july 26 and she said i would be about 3 1/2 weeks pregnant but the test is negagive. I need some help and answers. I'm only 18..