Negative test

Okay so me and my boyfriend have been using the "withdrawal method" for about six months now, yes I know that is very risky, but now we are actually trying to conceive. We had unprotected sex on December 30 which was the second day of my fertility window. I have been throwing up in the middle of the night, have have an increased appetite, have been extremely irritable, along with other possible symptoms. My period came on the day that it was supposed to which was the 17th of January but lasted only two days when it always lasts five. I was totally convinced I was pregnant and honestly still am but the hpt keep saying negative. Is there still a chance I am pregnant. If I conceived on the 30th of December, I'd be about 5 weeks now.