unprotested sex, emotional, tired... pregnant?

I was on ortho cyclen but my prescription ran out (and my doctor was on vacation) so I didn't take it for a month or two. My doctor then prescribed me ortho tri cyclen. I was less than a month into the new prescription when I had unprotected sex. My boyfriend didn't ejaculate in me, but pre ejaculation does contain a small amount of sperm. About two weeks later, I felt different. I got my period, but it was just different. And it started before it was supposed to. Anyway I took a hpt but it came back negative. But I've been feeling VERY sick in the evenings and am SO sensitive to smells. And I've been really emotional and tired. I'm pretty certain that I am pregnant, and yesterday I had some spotting that I'm sure was implantation bleeding. I took another hpt this morning but it was still negative. Did I take it too soon?