Spotting and Possible Pregnancy: What to Do?

Question
I am 20 and I have no kids.  I had my period a month and one week ago.  I have been feeling sick and two days ago I was bleeding a little, but I am not now.  I tought I was getting my period because mine is usually aorund the same time, but it is usually heavy and takes a couple of days. I have been very sexually active lately with my boyfriend.  I took pregnancy test over a week ago and it was negitive. My friends think I am pregnant because of the fact that I have to urinate much more lately and I have become much more hungry.  Is it possible i was spotting?  I really don't understand what spotting really is!  Is there anyway I can tell for sure if I am pregnant?  

Answer
When was the date of the first day of your last period? If you have a normal 28 day cycle (from the first day of your period until the first day of your next period) ovulation occurs on cycle day #14. YOu can only become pregnant if you have unprotected sex on cycle day #13, 14, 15, or 16. If you did become pregnant on one of those days, a pregnancy test will not show a positive result until 14-21 days later. The best time to take a pregnancy test is seven days after you miss your period. If it has been more than a week after you expected your period, and you have not seen the period yet, take a pregnancy test. If it is negative, you are not pregnant.