Delayed period, brown spotting after unsafe sex. Am I pregnant?

I am currently worrying as to whether or not I am pregnant. I am only 17 years old and was in no way trying to conceive, but hey, stuff happens. I am thoroughly against abortion but do not feel that I am strong enough to be a pregnant woman. I have not taken a home pregnancy test yet although my AF was due about 4 days ago. I seem to be too afraid to face the truth because I've just got this feeling that I am, that's why I've been so okay with putting off getting a test because I am almost certain that I am because I have never felt this way before or this in-tune with my body, it's quite strange. I do not remember the date of my last menstrual period but I am positive of the possible date of conception, which would be March 17th, exactly 12 days ago. 5 days after having unprotected sex, I got a brown spotting followed by two days of bright red bleeding. I thought this was my period, but it would have been a few days early. Strange thing is, this bleeding only lasted two days and followed by brown spotting just like before I began to bleed. I had never before had a period that lasted two days or have had such a bright red of blood. So I do not know whether to chalk this up as an early period or implantation/decidual bleeding since I did not get my period the 25th which is when my AF usually is each month (though I tend to have an irregular period alot.) I have read that a test is best about 14 days after conception so if I do not get my full blown period within 3 days I will go out and get a test. Unless you think right now is a good time where there is no possibility of getting a false negative because I do not want to go through this. I am just so scared and at such a crossroad & have no idea what to do with my life as of now