Could I possibly have a still born baby?

I have a 11month old baby already, I was on the Dep shot, from the time I had my daughter,I had 3shots of it, and then stop. I was suppose to get one done in June 2009. But never did go it done. I haven't had a period since May. I took a test, and it said negative, but I never took one again since July. Is the a possiblity that I'm pregnant, or had a still born? Can you carry a still born child and not have a period?