a little confused

my last period was december 6-9th of 2011, i was due for my period on january 3, 2012 but idid not get it. i did have some slight spotting on decmber 26th-29th of 2011. i am feeling very exahusted and having wierd stomach pains and my breast are slightly tender  to the touch. could there be a chance i might be pregnanat? my boyfriend and i did have unprotected sex a few times last week. im not due for my nex period untill the 24th of this month. im confused and if you can help me out a little that would be much appricated. oh and i also took a hpt and it came up negative, but still not sure what is going on with my body.