How To Confirm Pregnancy?

Basically my question is whether I should get a blood test to see if I am pregnant. I started taking birth control in January, and since then my period has lasted 3-4 days at the exact same time each month. Sometimes I forget to take my pills though, and my boyfriend and I don't use any other protection. A little less that two weeks ago, I was supposed to have my period, but I just had one day of light bleeding. Since then, I have been getting nausea over certain smells and from being in cars (which has never happened before). Also, my breasts are very sore, and I have to go to the bathroom all of the time. I have also been overly emotional a lot. I don't know whether I am just freaking myself out over nothing. I took a home pregnancy test today, and it tested negative.